I have the 125 gal
model and this worked for me...
1.Make sure the white filter in the bubble trap is all the way down in the cup.
2.When you put the black foam in make it level with the top of the bubble cup.
3.cut the outlet tube so it is ONE inch from white filter (making sure your bubble cup is 1/4 to 1/2 inch above the water line before cutting)
and this last one I did on my own and it decreased the bubbles even more...after the tube is cut and inserted into the bubble diffuser pull the black foam up the outlet tube so its about a 1/2 inch above the cup... works like a charm... Hope this helps.