For a 75 gallon tank,I wouldn't get one more than 8-10 watts....The quartz sleeve keeps the bulb itself from comming in contact with the water.This increases bulb life,and makes the unit more effective.Plus with a sleeve,you can change the bulb without shutting the whole system down.Just unscrew the endcap and take the bulb out.With a sleeveless unit,water would be pouring out...The wiper is a "wiper" that cleans the outside of this sleeve without disassembling the unit...Aqua does make a couple of Hang on the back(HOB) units that come with a pump.But generally,you do need a pump to run them.