How big is your system? Pumps come in different sizes and have different flow rates, so, obviously you don't want too small of a pump.
That being said, I just need some more info on what kind of hydro setup you want to run. Some water pumps efficiency are reduced when pumping vertical. So, is it a horizontal run like a bucket system or a vertical setup like a flood table?
I have plenty of answers for you if you're willing to get more specific on this post. I'll sub to this thread as well so I can help out.