Seeking Advice on Return Pump(s)

[EuroDriver]

I'd like your opinions and advice on whether I should improve on my pump system by modifying my existing setup or switching to an external return pump.

I'm doing a tank reset for several reasons, mostly ongoing algae and cyano issues which I'm primarily blaming on the very magnetic Hawaiian black sand I currently have. All of my livestock died with the last cyano bloom, so it's a perfect time for a reset and I'd like to take advantage to re-do some plumbing, since I am getting a dissatisfactory flow rate through my chiller.

My DT is a 180 with dual overflows (trapezoidal overflow on each end) and a Trigger Systems Sapphire CR44 sump.
I'm currently running 2 Apex COR 20's:
1st COR20-> IceCap40w UV sterilizer -> left return,
2nd COR20 -> JBJ 1/4hp chiller -> right return.
Left return is getting 350 gph flow while the right return is getting 175.

For flow in the DT, I have 4 IceCap Gyre 4K's and 2 Apex WAV pumps.

I am also running a reactor with RowaPhos and a Reef Octopus Elite 150-Int skimmer.

Taking advantage of the reset, I want to re-plumb the chiller to increase the flow rate (it should be around 400) and I also want to add 2 BRS reactors for the RowaPhos and carbon. My issues are that I really don't have any more space in the sump for additional pumps and the tank is running pretty warm (which I assume is from so many pumps in there).

Would I be better off with a large external pump tee'd off to both returns and gate valves to the reactors, or do something different with multiple DC pumps?
As an aside, I'm thinking of removing the gyre's and going with 4 WAVs for more simplicity in controllability (I have never been able to configure the Gyres to play nice with the Apex system). what are your thoughts?

Your advice is appreciated.

 

[mtnbike101]

Have you given any consideration for running a manifold? I have a single dc return pump (3500 gph) going through a manifold feeding both my UV and chiller. I control each return's flow rate individually.

Regarding gyres, I love the ReefWave 45's. They are so easy to disassemble and clean and the software is functional and stable. I do not attempt to control them or my ReefDose 4 via the Apex as the ReefBeat app does a fine job and I don't like putting all my eggs in one basket.

 

[EuroDriver]

I tried a manifold before adding the uv sterilizer but the flow rate was too low - perhaps because I was hell-bent on making it work with a single COR 20 at the time. Now that I'm actually considering a larger pump, it would make sense but unfortunately, I'm out of room in the cabinet below the tank.

I'm not opposed to pumps being programmed apart from the Apex but at a minimum, I'd like to shut them down during the feed/maintenance cycles along with all the other equipment