Best thing is to build something. The pentagon tank is a difficult shape to light properly unless you go with a MH
lighting because the tanks are rather tall as compaired to their surface area. The tanks not very wide across so you cant get the long higher output bulbs over it as easicly. I suspect the largest PC
bulbs you coudl put over that size tank is a 55/65W PC
and you would honestly need at least a pair if not 4 of those bulbs to properly light it.
Why not put a single 175W or 250W MH
pendant over the tank. Suspend the pendant from the celing above the tank. That would give proper lighting and be one of the most simple solutions.