hi, i have just made my own skimmer, 800 lts a hr pump 4" tube wooden block for fine bubbles. but as yet no" foameing," only been on for one day. i have put it in the sump the water in the sump is cryrstal clear i will have to see if my ammonia o, nitrite o, nitrate 40?. tank only 10 weeks old marine set up. the only thing i can think of is the tank is not to dirty?. ulosky