I want to add powerheads to get more circulation in my tanks. I have a 20 gallon hex and a 60 gallon. Both tanks are tall and I have a lot of dead spots. I want powerheads that are strong enough to make a good current that will kick up the poop but not too strong that my fish will be blown around. What gph do I need for the 20 gallon hex? What about the 60 gallon? Also any recommendations for a good relativley inexpensive powerhead would be much appreciated.