Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
When I clean the filter I just slosh everything around in a bucket of water drained from the tank. Larger filter or exceptionally dirty might need 2 buckets of water. The first bucket will be almost black. Gentle squeezing of sponges, floss. Slosh around the bio media.
Roughly half the bacteria live in the filter, but on all the media. Sponges, floss, on the surfaces of chemical media (for example, I have coral sand in some hard water tanks). The bio media is (in theory) designed for optimum water flow: Gentle so as not to harm the bio film, but continuous to constantly bring the bacteria the oxygen and ammonia they need. Thus, the coarse shapes with fine pitting. I do not know, within the filter, how much bacteria live in the bio media compared to on the surfaces of sponges and other surfaces. In part this will depend on how much of these you have. I do not have a lot of bio media, but I have a lot of mechanical media.
The other half of the bacteria live on all the surfaces of the tank. They do not like the light, but they need really good water movement, so you will find them on the top layer of substrate, on the leaves and stems, on the driftwood and rocks and ceramic merpeople.
To house a really large population of bacteria an object needs a lot of surface area, so fine gravel or sand will have a lot more bacteria than one large rock. A rock with a lot of holes (lava, Texas Holey Rock) will have a lot more bacteria than a smooth river rock.
Could the ammonia have come from the breakdown of chloramine? I know my water will test 1 ppm ammonia from chloramine right after a water change, but I know it is locked up by the dechlor. Not a problem.