Sorry to re-open this thread, but I'm a new member and don't know if this is ok. We're having the same problem, now we've had a tank for quite a few years 5+ years but it's more a hobby and we've never had problems with our tank, but we started seeing pimple-like things on some of our fishes fins, so we asked the local fish store what they were, we were provided medication for bacteria, and was told to remove the carbon and medicate the fishes, we did this along with WC.
We even purchased a smaller 2 ft tank to use as a hospital tank for the fishes that were bad. Hubby was then given 2 small red terrors which we put in the smaller tanks, but one of the red terrors died and the 2nd one is in a bad way, it has a long stringy poop, eventhough we haven't fed him for days, and after reading several threads and researching we realised that it was ammonia poisoning, now we were doing 50% water changes for nearly 5 days before our ammonia level for our 2ft got better, it's now better but still not 0, it's quite high at 4.0 but a substantial improvement to the 8.0 it was originally.
Anyhow, we decided to also test the ammonia levels for our 8ft tank although the fishes weren't showing signs of ammonia poisoning and found that our 8ft tank was just as bad 8.0, we've been doing daily 40% WC, using Stress Coat for de-chlorinating the water, and we've vacuumed all gravel, have not fed them and have vacuumed the tank and removed ALL ornaments, but the ammonia levels is still not getting better.
We are currently only adding aquarium salt and the parasite medication, apart from that nothing else is going into the tank apart from new water, does anyone know how we can lower the ammonia faster as it's just not decreasing
