I'm of the opinion that ALL fish require some aquatic based vegetation in their diet, just as they would in nature when consuming their fresh prey. The problem with many is exactly as Barrett stated:
However with the exception of perhaps a few top brands (which I don't have easy access to), both the quantity and quality of spirulina used in most fish foods is questionable (if not sometimes laughable).
The Cobalt food shown above is exactly one of those formulas, where there is more wheat, soy, and corn, than spirulina.
INGREDIENTS
SALMON MEAL, WHEAT FLOUR, SOY FLOUR, BREWERS DRIED YEAST, CORN STARCH, DRIED SPIRULINA ALGAE, FREEZE DRIED PLANKTON, FREEZE DRIED KRILL, DRIED KELP, FISH OIL, LECITHIN, GARLIC POWDER, DRIED EARTHWORM POWDER, VITAMIN A ACETATE, VITAMIN D-3 SUPPLEMENT, CHOLINE CHLORIDE, DRIED BRINE SHRIMP, L-ASCORBYL-2 POLYPHOSPHATE (SOURCE OF STABILIZED VITAMIN C), DRIED EGG PRODUCT, GARLIC POWDER, CALCIUM CARBONATE, VITAMIN E SUPPLEMENT, CALCIUM PANTOTHENATE, NIACIN, BIOTIN, RIBOFLAVIN, MENADIONE SODIUM BISULFITE COMPLEX, PYRIDOXINE HYDROCHLORIDE, FOLIC ACID, DRIED BACILLUS SUBTILIS FERMENTATION PRODUCT, DRIED BACILLUS LICHENIFORMIS FERMENTATION PRODUCT, DL-METHIONINE, NATURAL COLOR *NATURALLY CONTAINS ASTAXANTHIN
I love how they state;
NATURALLY CONTAINS ASTAXANTHIN
vs
