Pump and return advice

Since making use of my back up pump for my main tank I no longer have one and am looking at purchasing a new one and keeping the Mag 12 as the backup. Attached is a rough iso of the return system, the box is the overflow.

I need to know if a there is a better pump that would give me better circulation (pressure at about 3'). There is not a whole lot of pressure coming out of the spary bar and I'm sure that is because of the other 3 returns.

Two options I can think of:

First cap off two of the returns or remove the 3-way "T'", somewhat contradictory since I will loose some circulation.

Or I could put on a stronger pump and then reduce the outputs to add more pressure back to the spray bar.

Any suggestions would be greatly appreciated. Water flow would be coming from under and up the line in the top image, and it is 110 gal tank.

 

Buddy a spray bar is a total waste of time unless you want to pull it out and acid soak It every few months to keep it 1/2 way clean and the holes are always stopping up big time. You would be better off just using the 1800 as the main pump and maybe to shoot water water out of the 3 ports at the top or at different levels or better yet just drill and put a dedicated internal re circulation pump on the system for water movement but the spray bar is just junk to give you problems . On another site Yrs ago there was a guy preaching a spray bar LOL and Amcarrig put one in along the bottom rear to keep water moving to clear it out ! I told here then what was going to happen.. It did she will be the first to tell you it may look and sound cool on paper under Lab conditions but in the real world Its different . She had a dedicated mag 12 on that bar..

 

Should have just PM'd you! So get it out(the spray bar) and go with a MAG18?

Any chance that this is adding/causing my nitrate problem?