Discus Fish Filtration

Red checkerboard Pigeon discus fish

Why have filtration?

All our fishes wastes go into the water, so unless you change it regularly and filter it otherwise you’re beautiful fishes are swimming in their own waste and very quickly their aquatic world will become less than ideal.
You may have come across the term The Nitrogen cycle a good understanding of this is important to help you deal with issues with water and how certain chemicals can affect this cycle.

Essentially it goes like this..
The fish eat the foods we feed them and pass the wastes  into the water in the form of amino acids and peptides, bacteria then breaks this down into Ammonia > Ph7 and ammonium < Ph7.

This ammonia / ammonium is then broken down by bacteria in your filter into Nitrites and further by more bacteria into Nitrates.

The nitrates being ‘non toxic’ to fish at much higher levels than that of Ammonia & Nitrite which are leathal at even small quantities.

So the water may have in it suspended solids which we can see but don’t want as they look unsightly and these chemicals which harm or fish.

The normal way to deal with these waste products it to filter the water.

What type of filter to buy or make?

Internal Filters

Box filters

Placed inside the aquarium and can be run on air or from an electric supply, there are many on the market and the media you place inside is really up to you, you don’t have to stick with the stuff supplied with the unit and it is easy to change.

Sponge placed inside the aquarium and are run off air, these are ideal for small tanks


Not a massive capacity and may not take out larger particles suspended in the water & for a show tank they don’t look that good.

The external filter

Capacity not massive but normally enough for a single tank, two filters on the same tank is a great idea where one can be serviced whilst the other is in operation and still maintain good biological filtration.


Huge capacity for any media you prefer loads out there for pond use which is also ideal for sumps.


All equipment can be hidden in the sump leaving the tank free from clutter. This increases the capacity of your system and thus helps keep a more stable environment for your fish, large volumes of water are more stable than small.

Loads of them out there with the ability to insert different media, carbon, foams etc. They are probably the most widely used form of filter on the market.


They are costly to set up and only a few ready made on the market, dont be afraid though they are not that hard to make yourself.

The show tank normally has to be drilled to return the water to the sump, overflow weirs can be constructed though.

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