How to tell if there is bacteria in my filter

[Barry Tetra]

How do you know bacteria is in my filter, where does it live in/how do i get them?

 

[PheonixKingZ]

Is your tank cycled?

https://www.fishforums.net/threads/cycling-your-new-fresh-water-tank-read-this-first.421488/ <- Check out this thread. It helped me a lot. Do you have a HOB, internal, or canister filter?

 

[Essjay]

The bacteria we want grow in the biofilm which is attached to all the surfaces in a tank including the filter media. The bubbles in a sponge are a large surface area - imagine all the bubbles laid flat.
They get there because there are a few in the water supply. When a water supplier adds chlorine or chloramine they kill nearly all the bacteria but a few survive. We just need to grow a lot more of them and the best way for that is by doing a fishless cycle. Bottled bacteria products contain the same bacteria - or at least some of them do. Some have the wrong species of nitrite eating bacteria.

We know when there are bacteria in the filter and other places in the tank when we add ammonia and it is all gone next day, or when there are fish in the tank but there is no ammonia or nitrite in the water.