Hey there, looks like you're putting a lot of thought into your setup, which is great! Here are my thoughts based on some experience:
Gate Valve on the Return: I’ve used a gate valve on my return before and personally, I think it helps a lot in fine-tuning the flow, especially if you have an external pump. It’s a nice feature, but as you mentioned, opinions vary. It can be a bit tricky to dial in at first, but once you get it right, it keeps everything running smoothly. If you're worried about maintenance, maybe look into something like a union gate valve for easier disassembly.
Return Pump Size: 10x turnover is still a common recommendation for SPS tanks, but I agree with the second reply that 3-5x is often enough for most systems. It’s all about balancing flow between your return pump and additional equipment like your MP10s. Overdoing the return pump can cause unnecessary turbulence, so it's worth considering if you need that much flow.
Slip vs Threaded Fittings: I prefer slip fittings for ease of installation, and they also reduce the risk of leaks (especially when you’re working with PVC). If you’re building from scratch, go with slip, but if you need to disassemble things frequently, threaded might be better.
45° Elbows vs 90°: You’re on the right track with 45° elbows. They create less resistance and turbulence, which can be better for your overall flow and quieter operation. Definitely a good call there.
One Return: I think one return is perfectly fine as long as it's positioned well. As long as you’re factoring in proper flow from your MP10s and making sure the sump is set up to handle that single return, you should be good. If you’re building the tank to handle SPS, you’ll want to ensure water movement is consistent, but one return can work, especially with the right sump design.
Also, while you're at it, if you're looking for more specific plumbing advice or if you're going all-in on quality plumbing, I recommend checking out commercial plumbing services. I’ve seen great results with some of the solutions they offer, especially if you’re dealing with a more complex setup.
Hope this helps! Good luck with your build!
