CA2139054A1 - Self sustaining aquarium eco system - Google Patents

Abstract

The invention provides an aquarium system including a first tank for containing the fish and the second tank which is divided into two zones. The first tank includes a filtration system by which the fish excrement is extracted into an extraction zone leaving the fish within a fish zone of the tank. The first zone of the second tank is arranged to contain a composting action into which the fish excrement is injected by generating a waterflow from the extraction zone into the first zone. The first and second zones are seperated by a tank wall which leaves an open area through which water communication can occur. A return flow from the second tank to the fish zone of the first tank extract water from the area of the dividing tank wall. Within the second zone is provided algae and invertebrate animals which generate a swamp type environment. The extraction of the water adjacent the junction between the first and second zones causes only some of the invertebrate animals from the second zone to be withdrawn back into the fish zone for feeding the fish.

Description

- C~13qO54 SELF SUSTAINING AQUARIUM ECO SYSTEM
BACKGROUND OF THE INVENTION
This invention relates to a method of providing a substantially self sustaining aquarium eco-system and to an aquarium 5 specifically designed for use in the method.
SUMMARY OF THE INVENTION
The invention provides an aquarium system including a first tank for containing the fish and the second tank which is divided into two zones. The first tank includes a filtration system by which the fish 10 excrement is extracted into an extraction zone leaving the fish within a fish zone of the tank. The first zone of the second tank is arranged to contain a composting action into which the fish excrement is injected by generating a waterflow from the extraction zone into the first zone. The first and second zones are seperated by a tank wall which leaves an 15 open area through which water communication can occur. A return flow from the second tank to the fish zone of the first tank extracts water from the second tank at the area of the dividing tank wall. Within the second zone is provided algae and invertebrate animals which generate a swamp type environment. The extraction of the water adjacent the 20 junction between the first and second zones causes only some of the invertebrate animals from the second zone to be withdrawn back into the fish zone for feeding the fish.
One embodiment of the invention will now be described in conjunction with the accompanying drawings in which:

Figure 1 is an isometric view of a combined aquarium arrangement for use in forming a substantially self sustaining aquarium eco system according to the present invention.

CA2 1 ~ 9~

Figures 2 and 3 show similar schematic views of an aquarium system similar to that of Figure 1 but divided into two separate tank elements, the view in Figure 2 being taken from the front of the conventional aquarium tank and the view of Figure 3 being taken from the rear of the additional second tank.
In the drawings like characters of reference indicate corresponding parts in the different figures.
DETAILED DESCRIPTION
The aquarium tank system of Figure 1 is intended to be manufactured as a single item including both a first tank 10 and a second tank section 11. The tank 10 is basically a conventional aquarium the details of which will be described hereinafter.
In Figures 2 and 3 the same tank system is illustrated but in this case the first tank 10 is shown in Figure 2 and is seperate from the second tank system 11 illustrated in Figure 3. Intended that the system of Figures 2 and 3 will be used with an existing conventional fish tank 10 with the purchaser acquiring only the second tank section 11 for use with the existing fish tank.
The only differences between the arrangement of Figure 1 and the arrangement of Figures 2 and 3 relates to minor ducting directions as will become clear hereinafter. Otherwise the arrangements are identical and accordingly identical reference numerals will be used.
The conventional fish tank 10 shown in Figures 1 and 2 comprises a rectangular tank body having upstanding front wall 12, upstanding rear wall 13, upstanding end walls 14 and 15 and a base wall 16. At the base of the tank is provided a conventional filter plate 17 which includes a filter pad or tray on top of which is provided a layer of gravel 18. The filter plate 17 separates a fish zone 19 above the filter CA2 1 3~a5`~

plate and the gravel from an extraction zone 20 below the filter plate. In the conventional fish tank system, a flow of water is caused in the tank so that water is drawn from the extraction zone 20 and injected back into the fish zone after filtering from the water the fish excrement which is collected within the extraction zone. The filter plate 17 thus allows the fish excrement to pass through while preventing the fish and other large material from passing through and thus remaining in the fish zone.
In the modified system of the present invention, instead of the water from the extraction zone being returned into the fish zone, the water from the extraction zone is carried by a duct into the second tank. In the arrangement of Figure 1, a duct 21 passes from the extraction zone through the rear wall 13 of the first tank at the bottom of the rear wall adjacent the base wall 16 and communicates with a zone 22 of the second tank 11.
In the arrangement of Figures 2 and 3, a duct 21A passes through a tube 23 up and over the rear wall 13 and into a further tube 24 provided in the second tank 11 and extending down a rear wall 25 of the second tank into the same zone 22 which is provided in the second tank.
This difference of the direction of the duct 21 relative to the duct 21A constitutes one significant difference between the systems of Figure 1 and the system of Figures 2 and 3. The only other difference relates to the provision of an opening 27 in the rear wall 13 in the tank of Figure 1 which allows a return duct (described hereinafter) to pass through. In the arrangement of Figures 2 and 3, the same duct passes over the wall 13 since no such opening is formed in the conventional aquarium tank.

Turning now to the construction of the second tank 11, this includes the rear wall 25, a front wall 28, an end wall 29 and a second end wall 30. In the arrangement of Figure 1, the rear wall 25 is of course common with the rear wall 13 of the aquarium tank 10. The 5 second tank 11 further includes a dividing tank wall 31 which extends from a position at the top edge of the second tank to a bottom edge 32 which is horizontal and spaced from a base wall 33 of the second tank by a distance to leave an open exchange area between the bottom edge 32 and the base 33. The dividing tank wall 31 thus divides a second 10 tank into a first zone 34 and into a second larger zone 35. In practice the first zone is approximately one quarter of the volume of the second zone and the second tank has a volume of the order of one quarter to one half of the first tank.
The top edges of the tank at the first zone 34 are raised 15 upwardly from the top edges of the remaining walls of the first and second tanks by a short distance of the order of one inch to ensure that the material within the zone 34 is properly retained and does not escape by splashing or by other movements within the materials. In an alternative arrangement (not shown) the top walls of both zones of the 20 second tank are of increased height relative to the walls of the first tank so as to accommodate an increased water level caused by pressure differential between the inlet suction and the return suction.
A bottom wall of the first zone 34 is defined by an inclined tank base wall 36 which extends from a top edge 37 at the end wall 29 25 to a bottome edge 38 Iying directly underneath the bottom edge 32 of the tank wall 31. The base wall 36 is sealed to the end wall 29 and to the front wall 28 and the rear wall 25 so as to define a closed area underneath the base wall 36 and above the base 33. This area 22 is 5 CA2 139~54 generally triangular in cross section or wedge shaped and, as explained previously, communicates with the duct 21, 21A so that water passing from the extraction zone of the tank enters this area 22 underneath the zone 34.
The base wall 36 is connected to the tube 24 which is sealed to an opening in the base wall and to a further tube 39 similarly sealed to an opening in the base wall and upstanding therefrom. The tubes 24 and 39 are arranged at respective corners of the zone 34 adjacent the end wall 29.
A further tube portion 40 is attached into the corner of the zone 34 directly above the tube 39. The tubes 39 and 40 receive a conventional aeration tube 41 and soap stone 42 with the soap stone being received adjacent the bottom of the tube 39 and the aeration tube being guided by the sleeve 40 at its upper end. As is well known, therefore the soap stone 42 generates an air flow which bubbles through the water sitting in the tube 39. This induces an upward flow in the water causing water to be drawn from the area 22 into the tube 39 and ejected into the zone 34. The withdrawal of water from the closed zone 22 causes water to be drawn into that zone through the tube 21, 21A
thus generating a flow from the extraction zone of the first tank into the first zone 34 of the second tank. This flow is maximized by increasing the volume of air injected to the maximum available so as to generate sufficient water flow to ensure that the material is carried out from the extraction zone into the first zone 34. A discharge tap (not shown) is attached to the tank wall at the zone 22 to allow discharge of water from the tank for refilling with fresh water.
The second zone 35 includes mainly at the bottom the horizontal base 33 but in addition includes a short base wall 43 which is 6 CA2 13~054 inclined upwardly from the bottom edge 38 to a top edge 44. The base walls 36 and 43 thus form a generally V shape with a lowermost apex Iying along a line underneath the bottom edge 32. These surfaces thus act to direct falling materials to the bottom edge 38.
A return duct to replace water in the first tank 10 comprises a tube 45 having a perforated sleeve 46 at a discharge end thereof. The perforated sleeve allows the escape of water and foodstuffs carried thereby but prevents passage of larger snails or escape of smaller fishes.
It also spreads the escape of foodstuffs to prevent a single fish from monopolizing a single outlet. An inlet end 45A of the duct 45 is positioned at the bottom edge 32 on the side of that edge 32 within the zone 35 and adjacent the bottom edge 38. The open mouth 45A is thus positioned beneath the top edges 37 and 44 within the V shaped zone defined by the walls 36 and 43. The tube 45 extends by any convenient route back into the tank 10 to the discharge sleeve 46 positioned loosely within the tank 10. In the embodiment shown the second tank includes guide sleeves 47 and 48 which hold the tube in place. The guide sleeve 48 is mounted on the side of the tank wall 31 so as to ensure that the discharge sleeve 46 is held in the required position. The guide sleeve 47 is positioned adjacent the end wall 30 of the tank so as to direct the tube 45 upwardly toward the opening 27 as shown in Figure 1 or to a further guide sleeve 49 as shown in Figure 3.
The system thus comprises the three seperate zones including the fish zone defined in the tank 10, the first zone 34 of the second tank which acts as a composter and the second zone 35 of the second tank which acts as a swamp for growing algae and small invertebrates. The system further includes a source of light energy 50 shown schematically in Figure 3 for providing light energy to the zone 35. This can be provided by simply mounting the zone 35 adjacent natural light source or can be provided by electric light if required.
The basic principle is a flow-through system where the source of food is maintained and produced by controlling the flow of 5 oxygenated water. The system works by converting fish and higher invertebrates' detritus into plant material, converting the plant material into lower life such as monerans, protists, fungi and lower invertebrates which are then transported to the fish to repeat the cycle. The system must be provided with declorinated water and energy whether it be by 10 natural sunlight or artificial energy in the form of light bulbs.
The System consists of basically three compartments or systems, as described above:
The Aquarium (System l): It is the main storage basin for everything. It is our heat sink. It is our main producer of detritus. It is a 15 plant provider. It is a food provider. It also maintains a chemical equilibrium. The other systems alter the state of the aquarium water but the aquarium remains the reservoir. This is where new water is added and thus any imbalances are spread through a large body of water prior to being purified. It provides the room for larger or more advanced 20 members of the food chain to thrive, that is the fish and/or other larger vertebrates.
The aquarium is also a major food supplier. It will provide plant and decomposing materials for fish to eat. It will also supply snail eggs, organic life living off the detritus, as well as immature vertebrates 25 or baby fish and eggs.
But to my amazement it also supports and regenerates tubifex worms that can live completely under the gravel. However, they or their offspring will eventually become food for shrimp or bottom-8 CA2`1 3905~

dwelling fish. I believe that when setting up a new aquarium system, itwould be beneficial to seed a quantity of worms under the filter to speed up the establishment of an aquarium colony.
The aquarium is built along the concept of a flow-through 5 system. Unlike other conventional systems, the water is not stagnant.
The water comes in one end and comes out the other end. However the current in the aquarium must be fast for the under gravel filter to work efficiently. One of the hardest things to develop was getting the water to flow through the aquarium at a much faster rate than through the 10 swamp, which must flow very slowly so as to not disturb the various species that inhabit it.
With a flow-through system, you have changes in water temperature, chemistry, and nutrients from one end of the aquarium to the other.
There is no filtration system in the aquarium that must be replaced, cleaned or maintained. Nothing is filtered in the entire system.
Instead undesirable elements are converted to desirable elements to restart the cycle.
There is, however, a need to keep the water clear and 20 clean; if not for the benefit of the fish, but for the benefit of observers.
This is done through an under the gravel filter. The detritus filled water is drawn down to the bottom of the tank and under the filter. This water is then sucked from the bottom by an aerator in the second tank or feeder unit. Thus, in this system, the detritus is collected and not 25 discarded. In this system the water comes in one side of the tank through a feeder hose and is pulled to the other side of the tank by the under gravel filter.

CA21 39a~4 When the regenerated water comes in the aquarium the water has been recently aerated, oxygenated, filled with organic material, and full of food in the way of daphnia, tubiflex worms, eggs, small crustaceans, slugs and everything else that lives in a swampy 5 environment.
The highest part of your food chain is therefore not living in a stagnant environment but can choose to live in the part that it is most comfortable in with respect to temperature and quality of the water.
The benefit of the under gravel system is that it puts a 10 physical end to the food chain. The animals living in the aquarium cannot be sucked into the second or third systems. This terminates or blocks the free flow of life. However the detritus is still flowing to restart the system.
The Composter: The heart of the whole system. This is 15 where the water is pumped and the system is kept active and regulated.
This is the technical aspect of the system which we'll discuss later, but it is also a major source of food. Remember the tubifex worms we talked about earlier. Here they are produced in great masses for distribution.
What do they eat? Decomposing plant material and fish detritus, both of 20 which come from the aquarium. Earlier we discussed that all you have to do is remove some water and replace it with fresh declorinated water.
Well there is one more thing. Healthy aquariums always have lots of plant infestations, especially the small plants that float to the top.
Traditionally the observer would net these plants and discard them. Now 25 we recycle them by putting them in the composter. There they float to the top and make a very thick compound of decomposing organic material. There is no better place to raise tubifex worms than in the very food they eat and an oxygenated environment at that. Bacteria and 10 CA21 ~90~

other small animals decompose the rotting plants and fish wastes and the tubifex worms thrive on this bacteria. Plus they are provided with shelter and protection from their predators. An added benefit is that they are directly on top of the food dispenser or tray so whenever they fall from the nest they're fish food. Using this method to remove unwanted plant waste we can also recycle the nutrients in the systems as opposed to throwing them away.
The Swamp: is the key to the whole operation. We want the swamp as:
1. An Algae Scrub: To clean any chemical imbalances, diseases, bacteria, or overpopulation. In a sense it is a natural environment that acts as a thermometer. It is also the source of heat, light and natural energy.

2. A Composter: All waste from plant material, living organisms and fish is converted to living organisms, instead of being thrown away with the wool as in other filtration systems.

3. A Source of oxygen: The carbon produced by fish and other organisms such as the ones that decompose organic material are absorbed by the microscopic algae and small Monerans and Protist.
There are always thick coats of algae and other small plants growing in the gravel and on the sides of the glass. These also produce oxygen. Thus this system produces the bulk of the oxygen needed. It is the swamp. The place where water becomes new.

11 (~A2 1390~

4. A Source of food:
a) Tubifex worms. However as a source of food they are not a big provider at this point. Why! They are quite comfortable in this environment but they seldom make their way to the feeding tray. They are mostly eaten by snails, flatworms and other predators. Their benefit is that they shake up the decomposing detritus and put it back into the food chain.
b) Snails form an important part of the chain. Fish do not really eat them unless they're small. They do however like the eggs. Another way to harvest snails is to buy a clown loach which enjoys the sport of the kill but rarely eats everything he kills, thus providing tasty morsels for ghost shrimp or more aggressive fish that chase him away. This clown fish of course would reside in the aquarium part of the system. He would never run out of fresh snails.
c) Daphnia:(also known as the Water-Flea) In a word "The Food Source". There are many varieties and the more the better. They are an important link in the conversion of plant matter into animal food.
Their natural major predator is small fish. Daphnia multiply extremely fast. The young are carried in a brood pouch until they are released into the water as immature replicas of the parent. They become so numerous that they look like a cloud in the 12 CA21 39~54 water. The problem with Daphnia is they cannot tolerate currents at all. Thus there is not any current in the swamp. However at one end of the swamp where the swamp water mingles with the composter's water, there is a free exchange of water without creating a current in the swamp system as such. As a result a free exchange of daphnia occurs.
d) Fairy-shrimp. They would be an abundant source of food.
e) Gammarus (Freshwater shrimp) described previously .
f) Cyclops. They are found in large numbers. The male has well-developed antennae to grasp the female during mating and the female can be easily recognized by the pair of trailing eggs sacks on either side of her body.
g) There are thousands of species, however the one to be most concerned with are the daphnia.
Daphnia measure the health of the system.
h) Of course there are many species one would not want. Mostly you do not want predators; animals that eat your grazers; those animals that convert plant life to animal life. One would rather keep these grazers as fish food.
The system is basically a unique method of circulating water and nutrients, which does not discard any aspect of an environment but uses nature's own way of dealing with by-products to produce beneficial 13 CA~l 39054 products. This system is designed on a 3 to 1 ratio. For every three gallons of aquarium there is one gallon of Feeder Unit. Other ratios may work better, but this aspect of the design has not yet been fully studied.
The circulation system is based on the siphon principal 5 where water always tries to maintain the same level. To create circulation pressure is applied by an aerator in the composter to elevate this system. Water wanting to remain at the same level in the aquarium part of the system is forced to return to the aquarium. Thus we have a current.
The secret was to create a strong current in the aquarium to provide proper filtration and a very weak current in the swamp so mature animals would not wash away before being allowed to reproduce. In the swamp, water is only skimmed away. In this way, the animal population is maintained as only small numbers are harvested.
This differential water flow is created in the composter where all systems water is mixed. Water flowing through the aquarium is at the maximum speed the aerator will allow, while water in the swamp is barely touched. Water does not flow through the swamp.
Only a small part of the current is diverted to the swamp through the 20 opening provided and only ambient animals, plant and bacterial life is caught in this slight current to be pulled into the faster current.
The principle making the current is that air going up a tube will pull and push water with it. Since air is lighter it will always flow to the top and bring water along with it. This water comes from the sealed 25 feeding tray. The only other opening in the feeding tray is a siphon hose drawing directly from the aquarium. Thus water is being pulled from the aquarium and into the composter. In the composter it mixes with the water from both the swamp and the composter. Now the Feeder unit 14 ~a21 ~qn54 has a higher level than the aquarium. There is a siphon hose leading from the composter to the aquarium. Because the aquarium water is now at a lower level, water from the Feeder Unit returns to the aquarium. Thus we have a complete cycle and a continuous exchange of water, oxygen and animal life.
With the Add-On system, the tube from the under gravel filter must be extended to the surface of the aquarium. The intake siphon hose is then inserted in the tube with the other end leading to the feeder tray. This allows the water from the aquarium to be drawn directly from the underground filter thus causing a vacuum to suck up the fish detrius through the gravel and into the composter.
In the case of the integrated system, water is drawn directly from the under gravel filter through a hole in the aquarium wall into the feeder tray assembly. This creates a more efficient draw and adds to the aesthetic look of the aquarium by removing one of the tubes and siphon hoses.
The hose leading away from the composter is at the lowest point on the surface of the feeding tray, to collect the maximum food discarded from the composter and the swamp. In this way, a funnel has been created to suck up random samplings of animal life. By the use of the return siphon in both the add-on unit and the integrated system, the water level is returned to the level in the aquarium by forcing water through the siphon hose. Both the Add-On unit and the integrated system have a return siphon hose to continue the cycle.
Both systems can use either supplied energy, natural energy or integrated energy. To use natural sunlight, either extend the hoses on an Add-On system to put the Swamp and Composter directly in the window or, in an integrated system, move the whole assembly so that it 15 ~A21 39054 is in front of the window where natural sunlight is allowed to enter through the swamp.
In a multiple configuration system any number of Add-On units and Integrated units can be added in any combinations desirable.
The design of the system is simply a flow-through circulation device where various portions of the food chain can coexist and complement their needs without any part of the system being threatened by the needs of the other systems. What makes the system function is that the food chain flows only one way. The highest level of the chain, ie. The fish, are stopped from entering the lower levels by the under gravel filter. The gravel provides a break to prevent the fish from entering the composter or the swamp where they would devastate the populations of animals living in these systems. Only their detritus is allowed to continue the cycle.
1 5 OBSERVATIONS:
The first result I noticed is that the fish eating only live and scavenged food became healthier. No more big pot-bellied and lethargic fish. They became slick and fast. The fish aren't bobbing around anymore. They're hunting and always on the prowl. They scavenge different parts of the system. Most have, to a point supplemented their diet with some plants or rotting debris but when live food is put into the tank, you should see the drama!
The frog scurries out a tubifex worm. The platy steels a part away from him, while a painted Tetra dashes ahead of a black molly and steels a swimming daphnia moments before the molly's kill. You get the picture.
The food is introduced to the tank at random, as chance may have it. There is never a lot of food at one time but the food is delivered continuously. I believe this is probably the way nature intended it to be. What is also delivered continuously is microscopic food. These microscopic organisms are too small for the human eye to see and may also be too small for the fish to see but, when the fish take in water to 5 breathe, they also ingest these organisms, the foundation of the basic food chain.
The second result I observed is how very little work such a system can be. Imagine not adding anything to the system. Absolutely no maintenance other than replacing water that evaporates. When the 10 water level goes down 1 inch, simply remove 1" and add two inches of declorinated water. The rest is done for you nature's way. The ammonia and chemical imbalance in the water is treated by the plants and the microscopic life. The small invertebrates eat the plants and other decaying organic matter, including fish detritus. They are themselves 15 then eaten by fish to restart the cycle. Also within this balance there is room for error. Any imbalance that is detrimental to the system is absorbed by the system. It is best to let the system control itself with the minimum interference by the observer.
The third result came to me as a big surprise. I have long 20 had a deep appreciation of aquariums and fish. As a youth, I was interested in fish breeding. However I've of late been finding myself preoccupied with the invertebrates. Yes, they are mostly smaller than fish, but what a life they have. They are the most interesting animals to observe. Their life cycles are short, so you can witness whole colonies 25 multiply. You can see individual life be created and then be eaten by other life. Each species has different requirements, habits, and life cycles that can humble the observer.

17 ~A2 139054 A good example is the Gammarus or fresh water shrimp. It can be 1\2" long and is easily seen. It likes to swim upside down, but walks right side up. He's a scavenger, sometimes predatory if food is scarce. The interesting thing about a gammerous is that you most often don't see a gammerus. You see two gammerus. The larger female likes to piggy back the male. While holding him secure on her underside they swim along together in the search for food. Each and every one of these miniature animals has characteristics that can amuse you for hours.
The basic principle of the present system is to create an ecosystem or a self-controlled environment that will support life without the interference of Man. One might say "You're adding electricity".
Yes, for efficiency. But the system works equally well if instead of light bulbs you simply put a tank in a window frame and let natural sunlight be your source of energy. This is a new technology. What we're doing is not only sustaining life but creating life with no input except what nature can provide all on its own. The prospects for such a system can be many. I will offer some suggested uses, but can imagine many more.
The system has the following advantages:
FISH SUPPORT SYSTEM:
True to its "raison d'etre," the system will not only support fish but will make them healthier and encourage growth and reproduction. The added benefit of course is a near maintenance-free system.
A CONVERSATION PIECE:
Ecology-conscious people can build such a system and show their friends and kids how the environment works by converting the most elementary microscopic part of the food chain into higher organism.

18 CA21 390~4 A NATURAL STUDIES TOOL:
Science-minded individuals will try to achieve the maximum balance to better understand how the whole system works and can thus develop many improvements building on what has already been 5 developed.
A PRODUCTION FACILITY:
Marine life can not only be produced but harvested and incorporated in the food chain. An ambitious observer can use this system to produce marine life; such as "escargot", small fishes, shrimp, 10 etc. to be used as a source of food or saleable exotic pet supplies.
In concluding, I believe this system will not only be targeted at Pet Shop consumers but can be useful to a wide variety of people, especially since so much attention these days is concentrated on our dwindling natural environment. This is a new technology, one that 15 works, one that needs a lot of study and improvements and one that I
believe can benefit a lot of people.
Since various modifications can be made in my invention as herein above described, and many apparently widely different embodiments of same made within the spirit and scope of the claims 20 without departing from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.

Claims

CLAIMS:
(1) A method of providing a substantially self sustaining aquarium eco-system comprising providing first tank means containing water and fish living therein, defining a filter system in the first tank means allowing the passage of fish excrement therethrough from a fish zone of the first tank means to an extraction zone of the first tank means while preventing the fish from entering the extraction zone, providing second tank means containing water, providing organisms in the second tank means to cause a composting action in the second tank means, providing algae and small invertebrate animals in the second tank means, communicating light energy to the second tank means, generating waterflow from the extraction zone of the first tank means to cause transportation of the fish excrement to the composting action in the second tank means and generating a return water flow from the second tank means to the fish zone of the first tank means, the return of waterflow being arranged to transport therewith only some of the small invertebrate animals while leaving sufficient of the small invertebrate animals in the second tank means to subsist as a reproducing colony thereof.
(2) The method according to Claim 1 including dividing the second tank means into a first and a second interconnected zones and arranging the composting action in the first of the zones separated from the second of the zones.
(3) The method according to Claim 2 including injecting the water flow from the extraction zone into the composting action in the first zone.
(4) The method according to Claim 2 including withdrawing the return waterflow from the second tank means at a position in or adjacent the first zone so that water current through the second tank means passes substantially only through the first zone and generates substantially no current through the second zone.
(5) The method according to Claim 2 wherein the first zone is seperated from the second zone by a substantially imperforate tank wall leaving an open area portion of the tank wall open for free communication of water between the first and second zones.
(6) The method according to Claim 5 wherein the tank wall extends across a full width of the second tank means from a surface of the water within the second tank means to a position spaced from a base of the second tank means such that the open area is defined underneath a bottom edge of the tank wall.
(7) The method according to Claim 5 wherein the return waterflow is withdrawn from a position adjacent the open area of the tank wall.
(8) The method according to Claim 1 including providing an inclined base surface underneath an area in the second tank means containing the composting action such that materials falling from the composting action are directed to a lowermost portion of the base surface and arranging the return waterflow so as to be withdrawn from a position adjacent the lowermost portion to transport therewith the fallen materials.
(9) The method according to Claim 2 wherein the first zone is seperated from the second zone by a substantially imperforate tank wall leaving an open area portion of the tank wall open for free communication of water between the first and second zones, wherein the tank wall extends across a full width of the second tank means from a surface of the water within the second tank means to a position spaced from a base of the second tank means such that the open area is defined underneath a bottom edge of the tank wall, including providing an inclined base surface underneath the first zone in the second tank means containing the composting action such that materials falling from the composting action are directed to a lowermost portion of the base surface and arranging the return waterflow so as to be withdrawn from a position adjacent the lowermost portion to transport therewith the fallen materials, the inclined base surface including a first portion inclined underneath the first zone to the lowermost portion thereof underneath said tank wall and a second inclined portion on an opposed side of the tank wall means from the first inclined portion so as to define a base surface of the second zone inclined to the lowermost portion thereon underneath the tank wall.
(10) The method according to Claim 2 including applying the light energy to the second zone of the second tank means.
(11) The method according to Claim 1 including providing a colony of worms in the area of the second tank means in which the composting action occurs.
(12) The method according to Claim 1 including providing a colony of worms in the filter system of the first tank means.
(13) The method according to Claim 3 wherein the waterflow from the extraction zone into the first zone of the second tank means is injected into the first zone from an injection duct having an open mouth facing upwardly at a position partway up the first zone of the second tank means and spaced downwardly from the water surface thereof.
(14) The method according to Claim 13 wherein the first zone in the second tank means is defined by tank walls which have a top edge raised relative to top edges of the second zone of the second tank means and of the first tank means.
(15) The method according to Claim 13 wherein the water flow and the return waterflow are generated by injection of air into said duct so as to induce waterflow longitudinally of the duct.
(16) The method according to Claim 13 wherein the duct communicates with a closed area underneath the first zone so as to draw water out from the closed area and wherein there is provided means connecting from the extraction zone of the first tank means into the closed area underneath the first zone of the second tank means.
(17) An aquarium comprising a first tank means, a second tank means, tank wall means dividing the second tank means into a first zone and a second zone, the tank wall means having an open area therein for allowing free communication of water between the first zone and the second zone, a filter system in the first tank arranged to allow the passage of fish excrement therethrough from a fish zone to an extraction zone while preventing fish from entering the extraction zone, means for generating a waterflow from the extraction zone of the first tank means to the first zone of the second tank means and means for generating a return waterflow from a position adjacent the open area of the tank wall means into the fish zone of the first tank means.
(18) The aquarium according to Claim 17 including an inclined base surface underneath the first zone in the second tank means and outlet mouth means for the return waterflow arranged at a position adjacent a lower most portion of the inclined base surface.
(19) The aquarium according to Claim 17 wherein the waterflow from the extraction zone into the first zone of the second tank means is injected into the first zone from an injection duct having an open mouth facing upwardly at a position partway up the first zone of the second tank means and spaced downwardly from the water surface thereof.
(20) The aquarium according to Claim 17 wherein the first zone in the second tank means is defined by tank walls which have a top edge raised relative to top edges of the second zone of the second tank means and of the first tank means.
(21) The aquarium according to Claim 17 wherein an extraction duct communicates with a closed area underneath the first zone so as to draw water out from the closed area and wherein there is provided means connecting from the extraction zone of the first tank means into the closed area underneath the first zone of the second tank means.