Tell me why I can't use MH/T5 lighting systems designed for hydroponics?

[phillybean]

I have two 4' T5 fixtures on my tank with "Blue" bulbs. It gives the nice dawn dusk look. They are sunlight supply. In theory they don't have water proof plugs/end caps and I've heard of people getting shocked easily from them, although I haven't had any problems.

MH DIY Reflectors are fairly easy to make and DIY T5 reflectors can be done as well, although they are a bit harder.