Well guys have had my 20 gallon up for about 6 weeks. Went through an eternity of a bacteria bloom and it finally settled down about two weeks ago asof yesterday it was crystal clear and gorgeous. The filter had not been changed and was getting to the point of not flowing well at all. It was of course covered in healthy bacteria from nearly two months but I figured well perhaps there is enough in the gravel by now so changed it. Awoke this am to the signs of an early bloom, grrrrrrr cloudy darn!!!!! Would expect the velvet milky fog to really come in soon. Oh no!!!!!!!! It's only a beta and three corys and This was the weekend we felt all levels perfect to add a few more corys for my eight year old. I'll hit it with the small bottle of tetra start up which dropped all my nitrates at the suggestion of a very professional fish store. They k ow what they are talking about! So maybe 25 percent water change if at all and hit it with the bottle of live bacteria. Perhaps that will reduce what I expect to ne another many weeks of frustration ahead. Guess I should not have changed the big green filter. Any other ideas? Other than...duh! Thanks.