Are the tanks close together? In terms of calculations for them, it probably depends on the pump and your specific piping.
I’m not a good resource for plumbing issues though ;Brb
Are you wanting to achieve specific flow rates for the sump or for the returns to the tanks? I have never depended on my return for flow in the DT...I think of it more of augmenting the flow from powerheads. If you are just trying to evenly divide the flow from each tank to the sump I don't think I would worry about that too much. You could however install a gate valve on each tanks drain and measure /adjust to get them where you want.
Probably not understanding the question ....if so please disregard the above drivel!
Adam,
If you’re talking about flow from display through sump the old thinking is/was 10x display volume. The new is 3-6x.
Ime closer to 3 is better for 150 gallons or more, and closer to 6 for smaller.
If you’re not running a skimmer or refugium than closer to 10 is best
I have 2 tanks on qt plumbed to 1 sump.
I have 2 separate flow rates from pumps to each tank with 2 separate size overflows and drain pipes.
Same concept just smaller tanks than what you are trying to do.
It have its challenges like sump should be big enough to hold water in case of outage or pump/s shutdown.
Possibility of contamination reaching both tanks.
Double the effort and medications to fix problem in 1 tank which could get expensive very quickly as both ta is are 1 tank when it comes to fixing or medicating.
Equipment cost would also be a bit more as you will have to account for all the body of water. So bigger skimmers bigger filters bigger heaters etc.