Two things you might consider before using fish food as a gut load: 1) what's the animal protein content? and 2) what is the overall nutritional value? For gutloads, it is generally recommended to minimize or avoid animal proteins as they have been associated with gout and organ damage. Chameleons seem particularly sensitive to too much protein. Generally, fish food is probably either too low in vital nutrients or imbalanced for use as a base gutload. I would look into those two things on a product before committing to it.