I used to have AC110 and AC70 on my 90G. Then, I had to move AC70 to a timeout tank (20G) and my AC100 was getting way too loud (sending it in for repair under warranty). So I needed a new filter. I found a pretty good deal on fluva 405 on ebay ($130 including shipping), so I bought one and put it on last night. First of all, it is so much quieter, but surprisingly, the water clarity improved significantly. I did not expect that. Just wanted to share.