i am haviung almost the same problem as you, not that size tank but the ammonia levels are OFF THE CHART. i am also using ammo lock but on the bottle it says use 5ml for every 10 gal...so one capful for every 20 gallons then add every 2 days for seven days and if the ammonia doesnt go away after that then contact someone. ALSO i read on the back of the ammo lock bottle ....that the testing for the ammonia will still test positvie. it turns it into a non toxic form and and doesnt make it go away...but should be tested gone after the 7 days.... the pet store didnt tell me that it would still test positive no matter what you do....until the ongoing treatment is done.