Ammonia in QT

[OzymandiasXP]

I have a 10 gallon QT with a sponge filter and a biowheel HOB filter. No occupants (going on two weeks now). Last week there was high ammonia in the tank. I vacuumed the bottom to get rid of some old food, did a 40% water change, added some Prime and some cycle-booster to try to up the bacteria level. Ammonia dropped to 0 (using the API test).

Didn't touch the tank for a week and now ammonia is at almost 1 ppm. Any insight into what's causing the spike and what I can do about it?

 

[thegrun]

Is the tank only two weeks old? If so the tank is still cycling, expect it to take 4-6 weeks before the ammonia and nitrites stay at zero. If in fact the tank is cycling, you do not want to make water changes to reduce the ammonia, let it drop naturally as the beneficial bacteria multiply and process it. If the tank was already cycled something is seriously wrong, either with the test kit or you are having major die off in the tank.