GB2072523A

GB2072523A - A filter for a fish tank or pond

Info

Publication number: GB2072523A
Application number: GB8109742A
Authority: GB
Original assignee: Rhodes D C R
Current assignee: Rhodes D C R
Priority date: 1980-04-01
Filing date: 1981-03-27
Publication date: 1981-10-07

Abstract

In a filter for a fish tank or pond, contaminated water from the tank or pond is pumped to a filter vessel (1) and percolates downwards through a gravel filter bed (2). Purified water is drawn from a space (4) beneath the filter bed (2) for return to the pond by a return pipe (6) which has its outlet (7) above the level of the top of the filter bed (2), thus ensuring that the filter bed (2) is always covered by water and able to support bacteria essential to the purification process. <IMAGE>

Description

SPECIFICATION A filter for a fish tank or pond The present invention relates to filters for fish tanks or ponds, and is concerned particularly with a filter of the type in which contaminated water from the tank or pond is pumped to a filter vessel and percolates through a granular filter bed, for purification by bacterial action, before being returned to the tank or pond through a return pipe.

It will be appreciated that the term "tank" may encompass domestic aquariums, exhibition aquariums, and large tanks used in fish farms. It will be appreciated also that filters of this type may be adapted for use in swimming pools and water treatment plant.

Filters of this type acquire a population of bacteria and other micro-organisms which metabolize the organic waste products, particu larly ammoniacal material, in the water drawn from the tank or pond. In order to support the micro-organisms, the filter bed must be covered by water throughout its working life in the filter. In known filters of this type, the contaminated water enters at the top of the filter vessel, percolates through the filter bed, and is returned to the tank or pond through a gravity return pipe at the bottom of the vessel. The water level in the vessel has to be checked constantly to ensure that the filter bed is always convered by water, and the pump must work continuously to maintain this water level and prevent the bed from drying out.

The object of the present invention is to provide a fish tank or pond filter of the aforesaid type, in which the depth of water covering the filter bed is maintained automatically, even when the pump is inoperative.

Accordingly, the present invention provides a filter for a fish tank or pond, in which contaminated water from the tank or pond is delivered to a filter vessel and percolates downwards through a granular filter bed therein, purified water being drawn from beneath the filter bed for return to the tank or pond by a siphon tube which has its outlet at a predetermined distance above the level of the upper surface of the filter bed, thereby ensuring that the latter remains covered by water.

Although the filter bed may comprise any granular material capable of supporting the necessary bacteria, the preferred filter medium is gravel with a grain size of about 5 mm, which is easy to obtain and provides a filter bed with the optimum porosity.

The gravel, or other filter medium, may rest directly on the bottom of the filter vessel so that the inlet of the siphon tube is surrounded by the gravel, but in preferred embodiments the gravel rests on a perforated or mesh platform above the bottom of the vessel to provide a clear space into which the siphon tube extends. In some other examples, where the gravel rests on the bottom of the vessel, the inlet of the siphon tube may be sur rounded by, or comprise, a porous bell shaped member which rests on the bottom of the vessel and provides a gravel-free area from which the siphon tube can draw.

In most embodiments the siphon tube passes through the gravel bed and leaves the vessel at or near the top thereof. In some embodiments, however, the siphon tube may leave the vessel at the bottom and ascend on the outside of the vessel. In other examples, the siphon tube may be defined by a passage within a side wall of the vessel.

Typically, the filter vessel comprises a rec tangular cistern of plastics, such as polypropy lene, or any other water-proof material, but it will be appreciated that the vessel may com prise a cylinder housing a column of gravel.

One embodiment of the invention will now be more particularly described, by way of example, with reference to the accompanying drawing draping which is a vertical section through a fish tank or pond filter according to the inven tion.

As illustrated, a filter for a fish pond or tank (not shown) comprises a polypropylene filter vessel 1 containing a filter bed 2 of gravel with a grain size in the region 5 mm to 7 mm. The filter bed 2 is laid to a predeter mined thickness on a perforated platform 3 which provides a gravel-free space 4 at the bottom of the vessel 1. The size of the filter vessel 1 and the volume of the filter bed 2 determine the effective surface area of the filter which, in turn, is dependent on the surface area of the fish pond or tank. For example, a fish pond or tank with a surface area of 4 sq. m. requires a filter with a surface area of 1 sq. m. for effective filtration.

In use, contaminated water from the pond or tank is pumped to the filter vessel 1 through an inlet pipe 5, which enters at the top of the vessel. The water percolates down wards through the filter bed 2 where the gravel filters slit and other detritus from the water, while bacteria and other micro-organ isms, which colonise the filter bed 2 when wet, metabolize organic waste products in the water. The substantially purified water emerging from the base of the filter bed 2 is drawn from the space 4 beneath the platform 3 3 by a siphon tube 6 and returned to the pond or tank. The siphon action is initiated when the pump P is started, so that there is a continuous circulation of water through the filter when the pump P is operating.

In order to support the bacteria and other micro-organisms essential to the purification process, the filter bed 2 must be covered by water, or at least kept moist, throughout its working life. For this purpose, the outlet 7 of the siphon tube 6 is arranged at a predeter mined distance D above the level of the top of the filter bed 2. Should the circulation of water through the filter be interrupted, for example, by interruption of the power supply to the pump P, failure of the pump P or a blockage in the inlet pipe 5, the siphon tube 6 will continue to draw water from the vessel 1 only for as long as its outlet 7 remains below the level L-L of the water in the vessel.

The siphon action will cease when the water level L-L drops below the level of the siphon outlet 7, thus ensuring that the filter bed 2 remains covered by a depth of water corresponding to the distance D.

In order to maintain a steady water level L-L in the filter vessel 1, once the desired level L-L has been reached initially, the inlet pipe 5 and the siphon tube 6 have closely similar diameters. The inlet of the siphon tube 6 may be covered by a filter to prevent the induction of silt or other detritus, and the base of the filter vessel 1 may be provided with a removable plug to permit periodic flushing of the vessel. The vessel 1 may also be provided with a cover.

Claims

1. A filter for a fish tank or pond, in which contaminated water from the tank or pond is delivered to a filter vessel and percolates downwards through a granular filter bed therein, purified water being drawn from beneath the filter bed for return to the tank or pond by a siphon tube which has its outlet at a predetermined distance above the level of the upper surface of the filter bed, thereby ensuring that the latter remains covered by water.

2. A filter as claimed in Claim 1, in which the filter bed is formed by gravel.

3. A filter as claimed in Claim 2, in which the siphon tube draws from a clear space beneath the gravel.

4. A filter as claimed in Claim 3, in which the gravel rests on a perforated platform to provide the clear space.

5. A filter as claimed in any preceding claim, in which the return pipe passes through the gravel bed and leaves the filter vessel at or near the top thereof.

5. A filter as claimed in any preceding claim, in which the siphon tube passes through the gravel bed and leaves the filter vessel at or near the top thereof.

6. A filter for a fish tank or pond, substantially as herein described with reference to, and as shown in, the accompanying drawing.

CLAIMS (19/6/81)

1. A filter for a fish tank or pond, in which contaminated water from the tank or pond is delivered to a filter vessel and percolates downwards through a granular filter bed therein, purified water being drawn from beneath the filter bed for return to the tank or pond by a return pipe which has its outlet at a predetermined distance above the level of the upper surface of the filter bed, thereby ensuring that the latter remains covered by water.

3. A filter as claimed in Claim 2, in which the return pipe draws from a clear space beneath the gravel.