I have 2 aquaclear 30s in my 20g tanks. They have blown bubbles for a few months but now seem to have stopped. When I set up my 75g, I added an AquaClear 70 to supplement the Fluval 406 canister filter. The AquaClear 70 sits kind of high on the tank rim, so the return water has about maybe 1/2" to fall into the tank. There are a lot of bubbles, which I really don't mind, but the water has taken on a kind of dusty look. I think it is not particulate matter, but just the bubbles breaking apart and turning into much smaller bubbles. First question is, am I right about that, and second, is there any way to control the bubbling from that filter? The water looks basically clear and the water parameters are good. Any input will be much appreciated.