Asked By: Larry from Salt Lake City, UT
A: As long as you are feeding your pond fish a diet of high-quality fish food, they are unlikely to suffer from severe nutritional deficiencies. Fish absorb essential minerals from the surrounding water, as well as via dietary intake, making nutrient uptake easier than for most other animals. This absorption process, however, can lead to toxic overdoses of certain minerals like copper and selenium if you do not keep your water clean and balanced.
While scientists are certain that fish require “macrominerals (calcium, phosphorus, magnesium, sodium, potassium and chloride) and certain trace elements (cobalt, copper, iodine, iron, manganese selenium and zinc)”, fish nutritional science is an understudied field. As such, you should exercise caution when attempting to increase mineral concentrations in your fishpond to avoid overdosing.
The most common signs of vitamin and mineral deficiencies in fish include loss of appetite, slow growth, and skeletal deformities. Additionally, low zinc may cause cataracts and fin erosion, while insufficient iodine can contribute to muscular dystrophy. Other common symptoms of nutritional disease reflect those of humans and other animals, like anemia (low iron) and thyroid dysfunction (low iodine).
Luckily, The Pond Guy Pond Salt treats parasites and other infections that might be making your fish sick, while also supplementing electrolytes and improving gill function. Combine this salt treatment with balanced fish food and the trace minerals in The Pond Guy Clarity Defense all-natural pond water clarifier to prevent and treat most common nutritional deficiency diseases in fish.
More Common Fish Health Advice
If your fish are under the weather, whether from a nutritional disease or otherwise, contact us online or call 866-POND-HELP to speak with a compassionate pond fish specialist ready to help.
Read more about common fish ailments and how to prevent them below:
Last Updated: September 25, 2025