50 lb bags can be found at tractor supply-type stores and grain & feed mills. Wallyworld does carry fish feed, but in smaller packages and at higher unit cost. Their biggest bags are ususally koi food; I have been known to get cichlid pellets, krill, etc. there for the PBR.
I don't have the heart to subject our forum members to the wonder twins.
"Live like you'll die tomorrow, but manage your grass like you'll live forever." -S. M. Stirling