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Sponge filters are a cheap and simple to make biological and mechanical filter, perfect for fish tanks, temporary setups and quarantine tanks for new fish.
They are also cheap to run, and a low wattage air pump can provide filtration for several tanks simultaneously.
Very simply, air from an airpump is passed through an underwater sponge. Air bubbling out from the sponge to the surface of the water draws tank water through the sponge, cleaning waste from the water and also providing oxygen for beneficial bacteria in the sponge to grow and breakdown the waste.
As with all aquarium filters, the tank needs to be properly "cycled" (which can take several weeks) before there are enough bacteria on the sponges to effectively maintain the tank water.
Sponge filters are very simple to make. For small tanks, simply bore a hole into the sponge, put the end of the airline tubing inside and hook it up to an airpump. Air from the airpump will bubble up from the middle of the sponge, creating a current and drawing in waste, whilst providing healthy filter bacteria with the oxygen they need.
For larger tanks, two sponges can be fastened together with cable ties, and the airline tube sandwiched in the middle (as in the picture). By attaching an airstone to the end of the airline silicone tubing inside the sponge, you will create finer bubbles which improves oxygen diffusion into the water.
If you have any questions on how to make a sponge filter, please email me:
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