Filter behind the background

An aquarium is a bit of nature that you try to recreate in your home − in nature, you may find fish, plants, rocks, gravel and rotes, but not things such as aquarium filters and heaters. It is thus logical that you would not want to have to see these things when enjoying your aquarium, even if they are necessary.

The Back to Nature backgrounds are designed in a way that leaves sufficient space behind the background so that it is possible to hide all the technical equipment and also use the whole space as an enormous biological filter chamber that is effective for years without cleaning. Here is how to make one.

Planning the water flow

First we must decide on where to place a water inlet and a water extraction. It is important that these are far apart, because we want to use all space for filtration. Pictured below is the inlet on the left side and the extraction on the right.

Making the water inlet

Select where you want the hole for the inlet and then cut it out. You can use a drill or simply carve out the hole by hand using a knife. The sides of the hole are colored black using a water proof felt pen.

The water will flow in behind the background through this hole. The inlet hole is stuffed with a piece of coarse filter sponge, cut the sponge sheet larger than the hole itself for better fitting.

This filter foam sheet is covered with gravel for a more natural appearance. Take a look at the inlet solutions article for tips on how to make one.


Making the water outlet

Now carve or drill a hole for the water extraction. Use a drill bit with the same diameter as the outside diameter on the hose that fits onto the pump. The hole should be drilled just below the water level (you will have to estimate where the water level will be).

The water will flow out through the tubing on the front of the background. You can also use different output nozzles on the end of the hose in order to change the water stream direction as you want.

Place the technical equipment like the heater and a circulation pump behind the background. Connect the hose to the pump.

Arranging the filter material

A filter system can be arranged in several ways. Here we have used one sheet of coarse filter foam (PPI 10) 100 x 100 x 5 cm that is cut into small pieces of approximately 2 x 2.5 x 3 cm. Pour the filter cubes in the space behind the background, it must not be too tightly packed, because the water has to be able to flow through the filter. We have also squeezed in a couple of sponges on some spots where it’s narrow.


This is the filter system, viewed from behind the aquarium. The water inlet is on the right side, the outlet on the left side, and the space between is filled with filter foam. This will work for many years without needing to be cleaned.

These filters are more efficient than most filters on the market simply because of the larger filter volume. Investing in a circulating pump and filter media may also be significantly cheaper than for example external filters, and you don’t need to clean it.