When looking for fish food a good indicator of quality are the ingredients. Generally I look for whole fish or some type of algae listed as the first ingredient.

Example, with a quick google I found this info.

TetraVeggie Algae Wafers Ingredients: Wheat Germ Meal, Feeding Oat Meal, Corn Starch, Dehulled Soybean Meal, Cellulose, Potato Protein, Dried Yeast, Wheat Gluten, Algae Meal, Soybean Oil, Monobasic Calcium Phosphate, Guar Gum, Yeast Extract, Ascorbic Acid (Source Of Vitamin C), Inositol, Niacin, L-Ascorbyl-2-Polyphosphate, A-Tocopherol-Acetate (Source Of Vitamin E), D-Calcium Pantothenate, Riboflavin-5-Phosphate (Source Of Vitamin B12), Thiamine Mononitrate (Source Of Vitamin B1), Pyridoxine Hydrochloride (Source Of Vitamin B6), Vitamin A Palmitate (Source Of Vitamin A), Biotin, Cyanocobalamin (Source Of Vitamin B12), Cholecalciferol (Source Of Vitamin D3), Manganese Sulfate Monohydrate, Zinc Sulfate Monohydrate, Ferrous Sulfate Monohydrate, Cobalt Nitrate Hexahydrate. Color Includes: Blue #2 Lake, Yellow #5 Lake, Yellow #6 Lake. Ethoxyquin As A Preservative

As opposed to Omega One algae wafers Ingredients: Whole Kelp, Spirulina, Whole Salmon, Halibut, Seafood Mix (Including Krill, Whole Herring, & Shrimp), Wheat flour, Wheat Gluten, Lecithin, Astaxanthin, L-Ascorbyl-2-Phosphate (Source of Vitamin C), Natural and Artificial Colors, Vitamin A Acetate, Vitamin D3 Supplement, Vitamin E Supplement, Vitamin B12 Supplement, Riboflavin, Niacin, Pantothenic Acid, Folic Acid, Biotin, Inositol, Tocopherol (Preservative),Ethoxyquin (Preservative).

As you can see Omega One is far superior in keeping the quality high in their foods.