Originally Posted by namora
i'll look into the API kit, thanks : )
I know about the 1" rule, so i dont think i had too many fish. 4 i think at most
what does the beneficial bacteria look like? i've been getting really gross looking black sludge around the wheel where the water goes into the tank... but i'm not sure if that's supposed to be there
Four guppies or neons in a 6 gallon tank is not overcrowding. There is another source for the problem that we must find.
You mentioned that your ammonia and nitrite test strips looked good, but you also say the ammonia is high--what makes you think this? Which brand of water conditioner that detoxzifies ammonia are you using? As Arkamaic suggested, your tap water may contain ammonia. Unfortunately, some municipal water does have ammonia in it. Test a sample with your ammonia test kit to find out if that is your problem. If it is, you can treat the water with a water conditioner that detoxifies ammonia when you do your partial water change every week.
A partial water change of minimum 25% of the tank volume should be done every week. That will keep the aquarium more stable with respect to the water quality, and your fish will thank you. When you say "clean the tank" every two weeks, does that include the filter? The filter should only be cleaned when it needs it, that is, when the particulate matter is enough to impeded the water flow through it, and then just rinse it in tank water. The beneficial bacteria colonize every part of the filter as well as everything in the tank, and you want to preserve them. If you are thoroughly cleaning the filter every two weeks and using tap water you are killing off a lot of bacteria, and in a smallish tank with no plants that will cause ammonia to increase. I don't think this is the entire problem, not with only four fish, but it is another part of what may be the problem.
I know flake food labels say to feed three or four times a day, but that is not necessary for adult fish; fry need more frequent feedings, but mature fish can manage quite well on one feeding a day or even less if need be. As long as you're not overfeeding, twice a day is OK.
Another thought, what is the water temperature? It should be around 77F for guppies and neons. If your heater is keeping the water too warm (say above 80F) that could be a part of the problem, or the heater may be malfunctioning.
You can't see any of the bacteria, they are microscopic. I suspect the "sludge' around the filter is algae. It is common in all tanks, and tends to accumulate at the filter outflow. You can simply clean it off with an aquarium scraper or sponge, or even a razor blade and paper towel, when you do the weekly water change.
API test kits are good; the best is the liquid test kit, and they have one that includes ammonia, nitrite, nitrate and pH which is a good buy rather than buying them separately.
One of us will probably have more to offer when we have the above questions answered.