[dcarch]

Because fluorescent lights are considered "lineal source" not "point source" (incandescent type), therefore it does not follow the inverse square law of dissipation. In other words, when you increase the distance between the light fixture and say, your seedlings, the light intensity does not decrease drastically, especially if you provide reflective material around your lights. So if you want to simplify construction, you may choose not to have adjustable shelves or fixtures.

By the way, if you are making anything electrical, you should make sure that everything is ground properly. You can buy a ground checker, HD, fairly cheap, so you don't get electrocuted because there is always water around.

Don't forget to buy an automatic timer/switch.

dcarch