The number one ingredient most people feed their fish is fish meal. This is only because fish meal is the number one ingredient in most fish foods. This is primarily because of the ease and inexpensive sourcing of fish meal. However, the harvesting of fish meal is responsible for massive ecosystem and fisheries destruction.
The second ingredient is usually some kind of filler like wheat flour or barley. These are a poor sources of carbohydrates and only useful as roughage for herbivores like goldfish and koi. Some of the higher quality dry foods use whole ingredients like whole krill, shrimp or salmon and even add vitamins and minerals. These are great options and should be used several times a week.
Flakes, granules, pellets, and wafers are easy methods for feeding your fish, but so are whole, frozen options and they should be supplemented often. Frozen foods are cleaner, healthier, and closer to your fishes' natural diet. Let's break down what is in most common dry foods, higher quality dry foods, and frozen foods so you can make the most educated decision on how to customize your aquarium's diet to achieve the healthiest specimens possible.
Nutrition = Energy
Fish need protein, fats, carbohydrates, vitamins, and minerals to thrive. Cheap dry foods have little to none or poor sources of these nutrients. So lets stop feeding cheap dry-foods right now. The first two ingredients are trash. Even though fish meal is an excellent source of protein, there are other options that include every vitamin enriched part of the animal, not just the blend of viscera (guts) called "meal".
Wheat flour can be good for the digestion of a few species, but the vast majority don't need it, and it's a poor source of carbohydrates anyway. Finally, common dry foods rarely include added vitamins and minerals which are responsible for a fish's every metabolic function, not to mention their color.
High Quality Dry Food
But dry food is convenient, are there none of good quality? Luckily, companies are starting to catch on and are producing dry foods of higher quality all the time. When shopping for dry food always check the ingredient list and the nutrient analysis. Here is what to look for in order; (1) whole protein sources such as shrimp, krill, fish, mussels, brine shrimp, scallops, roe (fish eggs), (2) whole carbohydrate sources such as spirulina, kelp, chlorella algae, ulva seaweed, rice starch, and (3) additional nutrients like garlic, fish oil, beta carotene, vitamins a, b, c, d, e, k, and trace elements and minerals like potassium, magnesium, strontium, iron and zinc. You will most likely still find wheat flour on the label, just remember the farther down the list it appears, the better.
Okay, so cheap dry foods are not ideal, even the best brands still have wheat flour, now what? The best option by far is to supplement your fishes' diet with frozen foods. A lot of aquarists will make their own foods from fresh ingredients and freeze it for a truly customized diet. For now, lets focus on which pre-prepared frozen foods to supplement and when.
Feeding Schedule
For freshwater and saltwater tropical community tanks you most likely have top, middle and bottom feeders. Amongst them are probably omnivores, herbivores and maybe strict carnivores. Most fish don't need to eat every day. The exception being fast moving fish with high metabolisms or fish that graze on plant material throughout the day.
In a seven day week, feed frozen food every day, skipping two non-consecutive days, and high-quality dry food only once or twice. Feed your grazers every day with dry spirulina (saltwater) or fresh cucumber or dried kale (freshwater). Spot, or hand feed your most active fish every day with their favorite food.
The saltwater fish anthias, for example, need to be fed throughout the day, every day. This is how they eat in the wild and its the only way they will acquire the level of nutrition and energy they need.
Frozen Foods
When its time to feed frozen foods, there are tons of options. For freshwater insectivores (most small tetras, bettas, barbs, etc.) I would recommend daphnia or bloodworms. For Freshwater and saltwater carnivores I would feed whole shrimp, krill, sardines, Mysis shrimp, and cyclops depending on the size of the fish. Be careful if you use shrimp or fish intended for human consumption. There is a chemical preservative in whole shrimp that is not safe for fish and coral, but can be leached out by soaking in RODI water. It is best to buy whole frozen foods intended for aquarium use.
In addition to these single ingredient frozen foods, there are hundreds of varieties of frozen fish blends. My favorites being LRS Foods, Ocean Nutrition, and Piscine Energetics for saltwater, and Hikari and San Francisco Bay for freshwater. These blends achieve the same level of ingredient diversity as dry foods and are much cleaner (no whole wheat filler).
When done properly, your fish will receive all the nutrition they need to thrive with vibrant color and healthy immune systems. The key is to determine what your fish eat and how often, then provide the closest whole ingredient source. Insectivores eat insects, piscivorous eat fish, herbivores eat plants, etc.
In the end feeding a customized diet can be as simple or as involved as you like. You can feed all your fishes' preferred foods separately, or you mix them together in a slurry and feed all at once. Your fish and invertebrates will be healthier, happier, more vibrant and active, and behave more naturally.
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