Choosing Healthy Food for Your Fish
Fishes have two main metabolic processes: catabolism and anabolism. The former is the breaking down of metabolites to produce energy, while the later uses the same metabolites for building body tissue, growth, and reproduction. These processes are affected by the size, age, activity level, and general health of the fish among other factors. Metabolism in fish is similar in many ways to mammals, with two exceptions:
- Fish don't expend energy to maintain their body temperature.
- Excretion of waste requires less energy.
Fish obtain this energy through three main sources: fats, proteins, and carbohydrates. The diet of many fish in the wild, in fact, can be composed of up to 50% fats, and carnivorous fish may take up to 50% or more of their diet through proteins!
Ingredients to Watch For
FATS/LIPIDS: Fats are the primary energy source for fish, and keeping the right balance of Omega-3 and Omega-6 fatty acids is important. The best fats for fish foods come from aquatic sources, and whole fishmeal is preferred particularly menhaden.
AMINO ACIDS/PROTEINS: Too little protein can result in stunted growth in your fish, while too much or the wrong types may cause kidney problems and affect fish longevity. Good sources of protein to look for in fish food include: whole fish meal (menhaden & salmon preferred), unbleached wheat flour, cyclops, fish roe, squid/shrimp/cricket meal, spirulina algae.
CARBOHYDRATES: All fish are capable of digesting at least some carbohydrates, typically through plant matter, but fish that are primarily carnivorous are ill-equipped to process large amounts. Keep the primary natural diet of your fish in mind when looking at carbohydrate content!
SOLUBLE FIBER: Soluble fibers slow digestion and act as a laxative for your fish. Foods containing oat bran or barley, may be offered, along with fresh beans, peas, and some friuts.
ASH: Foods containing ash typically have a higher mineral content, especially calcium, phosphorus, and magnesium which aid in osmoregulation.
GARLIC: Garlic is believed to help boost the immune system.
COLOR ENHANCERS: Artificial colors have no nutritional value, and some may harm your fish. Look for foods that contain natural coloring instead: cayenne, saffron, marigold, paprika, etc.
Reading Your Labels
Often, labels on fish food don't give you the full picture. When the protein, fat, fiber, etc. don't add up to 100%, the unlisted remainder is often carbohydrates and sugars. Once you have this information, there are two primary 'rating' systems that can be used to determine the quality of a food.
The first method is to determine the energy rating of a food: whether its ingredients provide enough--but not too much--energy for your fish. This number can be determined by multiplying the combined starch, sugar, and protein percentages by 4, multiplying the fats percentage by 9, and then adding them together. According to a study by Clay Neighbors of Paradigm Fish Foods and AAP Custom Fish Foods, the target number should be about 280 for warm water tropical fishes; energy needs for cool water fishes are higher. PROS: This system is good for determining if your foods provide too little, too much, or not enough energy for your fish and whether your fish are at risk of liver problems caused by excessive protein. CONS: It does not take any other characteristics of the food into consideration other than fat, protein, and carbohydrate percentages.
The second method, named Oscarfish as a nod to the aquarium community forum that developed it, Oscarfish.com, ranks foods on a scale of 1 to 6 based on three basic criteria: 1) absence of toxic or potentially toxic, or controversial ingredients; 2) aquatic animal protein and preferred plant proteins as the primary protein sources; 3) includes necessary vitamins and minerals, with preference for natural sources. PROS: This system is fairly good at determining the overall quality of a food. CONS: It may sometimes be misleading, as foods containing primary protein sources automatically get preference with little concern for whether the proteins included are of the proper quantity; more is not always better.
No one system is perfect, and very few commercially produced foods have optimal energy ratings due to how they are processed, so I personally use something of a combination of the two systems, mixing and matching foods according to the needs of the species in each tank.
Observations on Food Ratings
With regard to energy point ratings on the foods I've personally tested in my aquariums, Hikari Algae Wafers, Tetra Bloodworms, and Hikari Sinking Wafers registered the nearest to optimal energy levels though all three were slightly higher than preferred (296, 310 & 321 respectively). Omega Shrimp Pellets, API Tropical Flake, and Tetramin Tropical Flake ranked the worst, with energy levels topping out at 368, 405, and 410; these three contain higher than average percentages of protein...which is not always better for fish. The biggest surprise to me though was Omega Natural Protein, with only 208 energy points; a number this low, while better for the health of a fish's liver, would need to be supplemented to ensure proper fish growth and reproductive health.
On the Oscarfish scale, the Tetra Bloodworms and Hikari Daphnia led the pack at 6 stars if only because as freeze-dried foods they consisted entirely of preferred proteins with no prohibited preservatives or artificial colors. Not far behind at 5 stars were Aqueon Betta, Hikari Sinking Wafers, Hikari Microwafers, and Hikari Algae Wafers which also contained no prohibited preservatives or artificial colors, but used fish meal as opposed to whole fish. Once again scoring at the bottom with just a single star was Tetramin Tropical Flake, which contains low amounts of preferred proteins and fish meal of indeterminate quality, as well as Ethoxyquin, Menadione Sodium Bisulfite, and artificial coloring.
Redeye Tetra Feeding on Daphnia
Observations on Fish Eating Behavior
FLAKES: Of the four varieties of flake food offered, API Tropical seemed to garner the best overall response through all aquariums though smaller fish needed to have the flake ground into a fine powder. Omega Natural Protein came in second, being more popular among the larger fish.
SINKING FOODS: The Hikari Algae Wafers, Hikari Sinking Wafers, and the API and Omega Shrimp Pellets were originally acquired to supplement the diet of my algae eaters and omnivorous bottom feeders. The tetras seem to have developed a liking for them though and will attempt to catch them before they hit the bottom of the tank. There doesn't appear to be a distinct favorite here.
FREEZE-DRIED: Due to their high energy content, I typically offer the Tetra Bloodworms and Hikari Daphnia as special treats. The best way to describe the reaction of the fish to these offerings is 'kids in a candy store!'
OTHER: The Hikari Microwafers set off an immediate frenzy when first introduced, unusual in my tanks for a new food.
Hopefully, you've found this information on the dietary needs of fish helpful in making an informed choice about what to feed your fish. Keep in mind that like a child offered a choice between veggies and candy, your fish might not choose the 'healthy option' on their own and may take some time to adjust to a new food or foods. But don't give up! You'll have happier, healthier fish in the long run!