I've never heard of this feed. You said you paid $36 per bag, but didn't mention the bag size. If its a 50 lb bag for $36, and its 45% protein, doesn't that totally annihilate Optimal and Purina?
I just found these for sale at Overton's:
https://overtonfisheries.com/cargill-premium-fish-feedThe prices listed are for direct pickup at their location, but it seems to be $40 per 50lb bag.