Fish disease diagnosis

Fish disease treatments

Koi ponds, aquaria & filtration



Freshwater fish


Filtration systems for ponds and aquaria

filtration home page

At the heart of most fish ponds and  aquaria is the filtration system. This might be a complex, large filter such as used with koi ponds, or a simple canister often seen with aquaria. Whatever the size or shape, filters work continuously to "purify" the water.  An understanding of filtration systems is important for healthy fish keeping

Biological filtrationNitrification
is a biological process during which nitrifying bacteria convert toxic ammonia  nitrate.

Sources of pollution

Often there is a failure to understand just how rapidly and to what degree koi pollute the water they live in.

Organic Pollution

This form of water pollution indirectly  affects koi health by encouraging high levels of opportunistic bacteria and parasites, as well as affecting overall water quality.

Removing solids from the system

If we could remove the solid wastes from the system before they had chance to dissolve and pollute the water we would have better water quality, less dissolved pollutants and fewer health problems. 

Biological filtration & filter media

What's the difference between the sometimes bewildering and conflicting claims made for various filter media?

Flow rates & retention times

Although a detailed understanding of filtration mechanics is not essential, this page does explain why some filters work better than others. There are a lot of over-stocked koi ponds with pretty poor filtration systems.


Fishdoc would like to thank the following benefactors for their sponsorship of this site: - Sho Koi - Aquadyne Bead Filtration - - Koizyme (Genesyz Aeromonas Fighter

Other Outbound Sponsor Links: