Some fish, called herbivores, only eat plant material and others, called carnivores, only eat meat; however, the majority of aquarium fish are omnivores, consuming both plants and meaty foods. Plant eating fish that are fed meaty foods cannot digest the food properly, leading to malnutrition, weight loss, and a rapid decline in health. If not fed the proper diet, a fish's life span is decreased substantially.
Although it is impossible to reproduce the exact diet that your aquarium fish would eat in the wild, you can provide a healthy diet if you follow some basic feeding guidelines.
With the introduction of dried flake, granular and pelleted foods, feeding aquarium fish has never been easier, yet every year thousands of fish become diseased or stressed because of improper nutrition.
Nutrition problems usually result from feeding the wrong type of food (plant based, animal based, sinking, and floating), feeding improper amounts (too much or too little) and the introduction of dangerous organisms when feeding live foods.
Supplementation with vitamins may help if you are aware of what food your fish should be eating, what you are feeding them, and the difference between the two.
Look at the fish food labels to make sure your fish are getting a balanced diet. Vitamins your fish need include: