So, we're all familiar with the fact that if you set up an external canister filter with medium for bacteria, benificial bacteria will develop in response to nitrite and ammonia in the water - right?

Here's my question.. if I have a tank with a simple in-tank sponge filter... and nitrite and ammonia are present, why don't those bacteria develop in the sponge filter/in the gravel of the tank and neautralise my nitrite and ammonia?

Sorry if it's a silly question, I just don't really get it

technically there will be some beneficial bacteria in both your in tank sponge and even on the gravel and decoration but the problem is that you dont have enough of them. the idea behind a canister is to house lots of this bacteria enough to convert all the amonia that your fish produce which in turn will eventually turn to nitrates.

i concur with cris on this. the porosity of the bio wheels
hold more good bacteria, thus, process more ammonia and nitrite

Oh so it is more of a question of amount.. The biological medium in the filter just has a larger surface area?

PhilK wrote:

yes sir. and they are placed in a portion wherein they could effectively convert ammonia and nitrite into a less toxic elements nitrate. and high nitrate could only be lowered by regular water change.

necromancer4 wrote:



x2............