Well the bubbles are what you want thats the co2, as they go up the ladder they are being diffused into the water, how many bubbles are we talking about here, how many bubbles every ten seconds or so are you getting? and have you any way of measuring the co2? if you do post the results, ideally you want around 30ppm if you are running a highlight tank>any tank running 2 watts per gallon or more.