This question has several answers.
The less expensive catfish food is usually made with soy as its protein source, which I wouldn't recommend as its generally the protein source already in your chicken feed. The higher end fish foods (such as Game fish chow) are much more likely to have fish/animal protein but I found them prohibitively expensive.
Adding in a bit of healthy animal protein and fat is usually a good thing as chickens are omnivores. Most manufacturers have removed the animal protein/fat and replaced it with soy as it is cheaper.
Like many others I toss my chickens a handful of dry cat food once in awhile. Its the Adult Cat Maintenance chow from Costco and has healthy animal proteins/fats. Kitten chow is not recommended as it can contain to much fat so if used, use it sparingly. Dog food is also not recommended but can't remember off hand what the issue was with that.
Also, it is recommended that a well balanced chicken feed be the bulk of what you give your chickens. The extras should be in small amounts even though they are in and of themselves, healthy. Snacks are just that, snacks. I would increase the amount of feed, and decrease the extra's you adding.
To add one more variable to the mix, is whether your chickens are free range or confined to a run. If free range, they will probably be able to balance their diet a bit. If confined, they are restricted whatever you give them and how balanced it is.
