Hey guys, Thank for all the suggestions!
1. I've set it up exactly the way the instructions say except I use purigen packs where the carbon goes and I'm substituting the Matrix for the bio rings. I think there may be too much matrix since it's a lot closer packed in than the 10 bio rings Fluval gives you(I hope that makes sense)
2. I'll use a 5G bucket and test with and without media...
Another thing to try is running it without the intake strainer.
Didn't think of that but I have small fish - I checked it and it's clean - I'm running the stock one so it shouldn't be an issue - I also took out the little ball that sits inside to help with the flow.
Check the white internal prefilter sponges, when my 206 slowed down they were the culprit. Crap seems to really build up in them and I found them hard to effectively clean.
Are you using after market pads on the top tray? If so some after market pads doesn't fit right and a tad bit smaller And it gets sucked up on the hole on the tray cover ,,,try putting the bio max on the top tray.
I was using two (one before and one after the purigen) - they were filthy with black sludge. I cleaned them out but I think I may just remove them all together because it was ridiculously clogged. It's almost as if the first sponge isn't catching anything - I honestly think this filter design is flawed with a lot of bypass - Do you guys have a lot of black sludge in your filters?
Definitely clean, clean and reclean or just replace those white tall sponges in the red tray, I didn't see the photo before but I bet that's your problem.
It's funny you mention those - they were spotless! Literally, just wet!
For the first sponge in the filter they were too clean considering the rest of the fine sponges were so thick with sludge. This is why I think there is a lot of bypass happening - The second reason I'm considering another brand.