You can run your tank w/out a GFCI and risk burning your house down. Or you can run your can with a GFCI and risk killing your livestock when the power is been shut off for too long. Your homeowner insurance might cover for the fire. Your homeowner insurance probably will not cover for a GFCI outlet tripping, killing livestock. Your homeowner insurance will not bring a dead, burn up childrens back to life.
I think the choice is clear cut. Get a GFCI to help prevent future house fire. You don't have to hook everythign up to the GFCI. You can leave one pump running on a non GFCI outlet.
Look at all those live rocks on the beach at Florida's state park!