Thanks for your help, so I was planning on running "2 x 3000L/H pumps" so I have something for redundancy giving me 6000L/H turnover which is a bit over 5x per hour, but your right I should probably be looking at something larger and "variable" so i can change it as I see fit, I will add it to the "to do" list tomorrow.Most of what you are asking is way above my pay grade, but I would go with higher capacity pumps. There are very efficient variable speed DC pumps available that allow you to customize your flow rate. I am using a Jebao DCT-15000 at the lowest setting which I believe is 40% max or 6000 L/H on a 210 gallon aquarium. I would think you would want around a 5x turnover on your project so a single unit like this could work or you could run 2x pumps at lower settings and have some redundancy.
Cheers