Competitive Exclusion

What is it?
Competitive exclusion is a term used in aquariums to keep pathogenic (bad) bacteria in low levels in an aquarium or pond.

By adding known harmless waste eating bacteria in large numbers the added bacteria out competes any existing bad bacteria for the nutrients in the tank and therefore is a safe and effective way to starve off infectious bacteria. In the medical industry this technique is called 'bacterial interference' and is used to displace pathogens by using harmless bacteria.

This is a successful way for beginners to keep your fish healthy. In a new tank there will be virtually no bacteria to out-compete bad bacteria that may be in the fish's gut. So with micro-particles of fish food floating down to the substrate, the bacteria from the fish, ornaments and of course the aquarists hands are all a huge food source for bacteria and are able to grow with no competition from anything else.

By adding harmless bacteria from a commercial bottle in large quantities, you starve off the bad bacteria by sheer volume.


 * This method also reduces maintenance on your filter and helps keep the gravel cleaner as the bacteria consumes all decaying material and breaks down dead plant matter that would otherwise take weeks to breakdown. This method is commoningly used in human sewage treatment to break down human produced mulm.


 * This method is why having a soil based (Walstad) tank is so successful. The soil has tens of thousands of species, with billions upon billions of bacteria in it which keeps pathogenic bacteria levels very low.

Typical products

 * Koizyme
 * LymnoZyme
 * Waste Control by Nutrafin
 * Biozyme
 * Waste-Away & Eco-Balance
 * Stress Zyme by API
 * Stability by Seachem
 * EcoBio-Block
 * Viresco Aqua or Viresco Koi
 * MicroBacter7

How it works

 * Article on the Keeton Aqua web site on its benefits.
 * Case studies on using commercial bacteria to remove pathogens.


 * Patent details of one of the above products LymnoZyme