Pump too strong.....

It will be louder from the high velocity entering the sump. This is a bad idea and has been proven for decades.
Most centrifugal pumps get more efficient when you add head like with a valve in the return line. Adding the tee does the opposite and reduces the head increasing the flow and raising the power requirements and work being performed and importantly the heat generated by the watts consumed. Its hard to understand but is spelled out in Bernoulis Theory and The Laws Of Affinity which both apply to all centrifugal pumps.

 

If you truly are using the foam filter, than remove it as that is the cause of your problems. I don't think there is any way a PF-800 can't handle the flow from your MAG 9.5 if it's dialed back even a tiny bit. I have a PF-300 and a MAG 3 running wide open and it's not even remotely close to a problem. So, you should not need to throttle back a MAG 9.5 almost all the way.
Also, as previously mentioned, lower your overflow box a little bit. If it's set too high, you can get very close to overflowing the DT (or maybe even overflowing if it's way too high). That could also be your problem. Try one or both suggestions and report back.

 

Pictures of the set-up would make it a lot easier to figure out the problem. I personally don't think it is the foam filter or height of the filter box, but it is really difficult to diagnose based on your description.

It is not an equipment problem though, it is a set-up problem, so don't stress out about buying the wrong pump and/or overflow. Plenty of people have similar overflows/pumps as you, and have them work without problems. Jeff from Lifereef recommends Mag9.5's on all of his 600 gph overflows, and he is very experienced with u-tube overflows.

 

Pictures of setup added

I have added a lot of these photos. Excuse the poor camera quality. You can see the air bubble in the top of the U-tube overflow. It is suprising that is can stay siphoned with that much air. The moment i turn my pump up, it is pushed out however the overflow wont keep up with the pump and the water level continues to rise in the tank.

The sump is setup with a 1" overflow drain that splits into two drains (i added the "T" and the 1" ball valve when I thought i was oging to use a refugium (will do down the road). The return pump is really throttled back quite a bit as you can see and it goes up using only 45 degree pvc all the way to the top and eventually splits into (2) 3/4" loc lines.

 

Additional Photos

 

Ive read that the foam that the eshopps overflows come with are not to be used but are packed with the box so the u-tube doesnt break. Cant remember where i read it.

 

I am not even using the foam now and if i turn my pump up anymore the overflow cannot keep up and the display will flood.

 

okay, from the pictures you can see that air bubble in the u-tube, is that always there? What i did when i had mine is I always kept a little airtube in their so i could suck out the air, you should get better flow that way.

Sorry if this has already been covered.

 

The problem is.... Eshopps overflows are designed that you should not have any air bubbles in the U-tube. Once I start the siphon, I should not have to maintain and suck any air out. The pump should be able to pump fast enuogh it pushes the bubbles out before they can collect. However since my overflow is NOT keeping up with my pump, I have to have it throttled back suppppper far.

 

Remove the t from the overflow pipe and just plumb it straight down from the 45. The t is likely causing the problem and restricting the flow along with the other 90 and 45's.