Rainbowfish, guppies and swordtails need some plat matter in their diets. Rainbowfish in particular need about a diet with about 50% plant matter. This can be actual aquatic plants like Duckweed and Ambulia, or vege flakes/ pellets and goldfish foods that have more plant matter in.
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If you use a vitamin supplement, use a dry powder form and keep it cool and dry at all times.
A lot of vitamins are water soluble and break down in water. Heat also destroys vitamins.
Using a dry powder vitamin supplement can help fish if there are sick or not getting a well balanced diet. You sprinkle a small amount of the vitamin powder on some frozen fish food, mix it in and then feed to the fish.
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Fish should be fed a variety of foods to maximise their nutrition intake, and to prevent them going on hunger strikes if their main food is no longer available.
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Fish do best when fed dry, frozen and live foods. The main live foods to avoid include Tubifex worms due to where they come from (sewerage farms), and bloodworms (Chironomid midge larvae) that have extremely hard heads that can't be digested by most fish.
Most other live foods are fine and brineshrimp (adult & newly hatched), daphnia, micro, grindal & white worms, small earthworms, aphids, mozzies (larvae & adults), small flies and moths, weevils & larvae, etc, are all good foods.
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Frozen foods are fine and the above list (brineshrimp, daphnia, etc) are all good. As is prawn, fish and squid/ octopus.
Some brands of frozen bloodworms are collected from sewerage farms and can cause intestinal bacterial infections in fish. Some brands are irradiated and are generally much safer for fish. Some people are allergic to frozen bloodworms and you should always wash your hands with warm soapy water after using them, or any frozen of live fish food.
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There are numerous types of dry fish flakes and pellets. Some are good and some are not as good.
Try to avoid getting fish foods with flour in them. Most manufacturers put wheat, corn or soy flour in the fish food to help bind the ingredients and to bulk it up. Flour is cheap and can be used to add weight to the fish food so the manufacturer can charge more for a heavier product. Fish can't digest grains so any fish food containing wheat, corn, rice or soy flour should be avoided, especially if the flour is in the first 5 ingredients.
Good dry fish foods for predatory fishes should contain fish and prawn as the main ingredients. Then some algae is fine.
Dry foods for vegetarian fishes should contain algae as the main ingredient and then fish, prawn and small crustaceans like daphnia, cyclops, etc.
Some companies add vitamin supplements to the dry fish food. Some of these supplements can be helpful as long as the dry food remains perfectly dry. However, dry flake foods absorb moisture very quickly and this can cause the vitamins to break down.
Some companies add herbs like rosemary, garlic, lavender, etc. These are useless for fish who can't digest them. Basically fish can't digest terrestrial plants very easily and should have aquatic plants and algae, not terrestrial plants.
Most colour enhancing fish foods have paprika to enhance red and orange in fish. You can buy colour enhancing foods or use paprika, blueberries and apricots, carrots or pumpkin to enhance colour. Get the fresh fruits and veges and squeeze the juice onto some frozen food. Let it soak for a few minutes then feed to the fish.
