the tank is a 90 gallon with wet/dry system, and yes the bio balls are still in it...with a skimmer and 200lbs of rock.....its 1 1/2 years old, and the only time that i have had problems with nirates is when i used the kill hair algae stuff and it did kill the hair algae but it also made my trates go off the charts....took about 4 months to get them back down, but no problems since and i added 100 plus new blue legged crabs and hair algae is gone...thanks for all the good words