Glad i saw this post. I have a 125 and I am having the same problem!!!
I am finding that I have to open up the bps dial ALL the way open with the PSI set VERY VERY high like more than half way (cant remember the numbers off hand as I am at work now).
Anyway, I am getting tons of bubbles and burping in the tank. Forgot to mention that the reactor is running off an Eheim Pro 3 2180, 450 gph.
So I take the bottom line is either a bigger canister or a T valve for a double return?
I too wrote several emails to aquariumplants.com and never got a response. Wonder what happened, they used to be pretty good.