Regarding hanging the fixtures, you can use hooks and light chain which can be found at places like Lowe's or Home Depot and hang them from the ceiling.
To attach the chain to the fixture you can use a small eyebolt (not the screws) with a nut and washers. Drill a small hole where you want to attach the eyebolt and attach them securely. The chain links should bend enough to place the eyebolt into the link and then bend back to lock it into place.
Make sure the hooks in the ceiling go into the roof joists, not just into the sheetrock or whatever you have on the ceiling. Otherwise, the fixtures could fall.
Another option is to use plant pot hangers attached to the wall (if you can find some long enough), again suspending the lights from the hangers using chain and eyebolts and using rings instead of hooks. Be sure to attach the hangers into the wall studs for security.
Yet another option is to build a mount that stands on the floor and goes over the tank. You can attach the lights to the frame, plus this gives you the added bonus of being able to secure the wiring to the frame as well. It also doesnt put holes in the wall or ceiling which would have to be patched if you relocate the tank.
