any good resources out there on how to pick the appropriate size pump?

i'm building an aeroflo style system with a total of 5 or 6 four foot tubes, with a total of 30 or so plant sites. there will be two nutrient reservoirs, one for vegetative growth solution and one for fruiting solution, so i can swap the tubes from one to another as necessary. one pump will need to service 3 of the tubes, max.

two 4" tubes with plant sites every 6" (for lettuce, herbs, seedlings, etc...) and 3 or 4 5" tubes for larger plants, with plant sites every 8 - 12 inches.

about 3' of head.

thoughts?