Ok so I'm designing a sump/refugium out of two 20 gallon aquariums. I was planning on having the returns from each tank meet up and return to tank. Would four pumps be too much pressure. I say four because i would think i would need two in each tank in case one fails. I am going to split the overflow (ball valve) to each tank, one a sump with all mechanical and chemical filtration and the other with refugium and biological filtration. Looking for suggestions on the return setup