I feed Aquamax MVP and several Optimal feeds. The Aquamax is hard to beat for the quality/price relationship, but I really like Optimal for the smaller quantities of specialized feeds that I can easily order one bag at a time and have delivered to my doorstep. Trying to get small quantities of specialty feed through Purina is about as pleasant as pulling teeth.
Both are good feed.
Purina does make some lower protein feeds more for recreational feeding rather than growth, but I would stick with the higher level Aquamax.
Here is a
thread with feed information and links. 
