It depends really, is this for a display tank or a little project in a spare room for example?
You threw me by saying "its only a clearseal" I took it as you not being bothered about looks and it was hid away or something lol
If this is the case all you will need is a T5 ballast, a bulb and reflector. You'll need some way to mount it too.
If you want it to look half decent you're going to need a luminaire or pendant type thing. These are available with just one T5 bulb, I personally haven't come across a lot on my travels but they do exist. Having a search around google or eBay would probably be your best bet.
Failing that, 2 x T5 pendants are pretty common so you could go with that and just run 1 bulb if 2 proved to be too much.