Hey guys, thanks for the answers... i havent replied sooner cause i stoped being noticed of replies... strange.

Anyway, i have solved the problem of airlocking by puting the CO2 hosea little of the entrance of the pump, so it can suck the gas only when it is on. If i can borrow a camera, I ll post some pics. I have tried the ventury, but to no sucess.

Well, in the meantime from my last post, the algae is under control - I was having a terrible bloom of green water - and I haven't done anything about the indirect sunlight, jusk kept high CO2 and ferts. I guess the indirect light doesn't affect the aquarium as much as I thought.

After years of resistence I have tried the yeast method, and have been using it ever since, mainly because it's so easy to refil.