Hi....One of my 10 gallon is about 3 weeks old...and when I test it & it always has high levels of ammonia even when I do large water changes. For example...if I change 90% of the water and fill it up with new water I test it a second later and the levels are the same. I also do water changes very often to keep the ammonia levels down but it doesn't help. Am I removing benefitial bacteria by doing large water changes very often? Someone suggested I only do water changes once a week and the ammonia should lower. What do you think?