Red Sea Max 170 Setup/Adjustment?

[snowdude78]

I recently purchased a used Red Sea Max 170 to replace a take that started leaking last week and I'm having trouble figuring out how to adjust all the adjustments.... The protein skimmer (stock) and rear sump are all new to me and I haven't been able to locate any documentation on how to properly adjust any of it. 

 

It seems that both the flow gate and the air valve on the protein skimmer have an effect on the sump water level, but I have no idea how to properly set them (more so the flow gate on the skimmer, I assume once that's set properly you make small adjustments to the air valve to get the proper skim rate. 

 

I originally had a canister filter on my old tank which did a really good job of removing fine particles from the water, but it seems like the overflow system doesn't have a way to remove sand in the water other than letting it slowly (very slowly) settle from the water over time. Is there something I'm missing?

 

When I look in the output side of the rear sump, the water on top looks stagnant like the flow is incorrect. There's stuff floating on the top on that side but there is definitely water flowing from the output nozzle, so it almost seems like maybe somethings setup wrong?

 

Any help is greatly appreciated, I really want to get things working properly, but so far it almost seems to be less effective than the $50 canister filter I had on my old tank.