Feeding your fish frozen perch would not be bad, even as a staple diet. Perch are not as high in fat as feeders and bait fish and are more nutritionally complete. Were you thinking of feeding whole or just filets (whole would be better-as they are more balanced). My redtail eats whiting filets with a few krill and carnivore pellets. I feed whole shrimp, beefheart and small convicts (hope that doesn't offend anyone) as a treat every now and then.