My QT tank is having ammonia problems. I've been treating it with ammo-lock, but I see no reduction at all in the ammonia from one day to the next. I've been doing daily 50% water changes with aerated and heated water. I tried to kickstart the biological filter like I did the last time I had the QT up and running by adding about 15 bioballs to the filter chamber of my powerwheel. I've been testing daily for ammonia, nitrite and nitrate. Ammonia goes from about 2 ppm after a water change to around 8ppm after 24hrs. This seems like a massive increase to me and there's only 1 fish in there!! When I had ALL of my fish in that QT for a month, the ammonia never got above 3ppm (at which point I did water changes). I picked up some saltwater BioZyme from petco which is supposed to be a good bacterial culture for seeding filters, but with undetectable levels of nitrite or nitrate, I think I can safely assume that there's no biological filter activity. The last time I ran the QT I had some maracyn 2 in there, but when I broke the tank down I rinsed it out with DI and toweled it off to remove any left over debris. I added an activated carbon sock to the filter last night to suck out any remaining antibiotic. I just can't understand how I can run the tank for a month with 6 fish in there and now I can't even keep one in there without an ammonia problem. My last resort is to go pick up a new QT tub from walmart just in case I didn't clean it out well enough after the last QT round. Any ideas?