More turnover is good, more flow is bad. Unfortunately with the Marineland biowheels you can't turn down the flow. With a canister, you need a spraybar b/c the seahorses definately can't handle the flow from one of those without it. That being said, cannisters are still a good idea. So are refugiums. I don't know the exact wattage you need for your LR, but often people recommend the wattage to grow the purple coraline, but the rock doesn't need coraline to be alive. Definately get at least 1 pound of LR per gallon of water. The requirements for a seahorse aquarium are different from that of a reef aquarium. I suggest you double check all of your ideas at
www.seahorse.org.