Viper,
No, the brownness is gone thanks to a really big water change and a good vacume.
No, I'm not getting any foam. I adjusted the water level to be more in the neck of the cup to see if it will speed it up.
Alan,
I removed the powerhead it came with and added a slightly stronger pump. Then, I removed the venturi and modded the pump to rather suck air in to be chopped up by the impellor. The resulting bubbles are much much finer than with the opriginal configuration. I was thinking, can the bubbles be too small?