As your fish come out of their winter dormancy and are fully revived, they will require food that meets all their nutritional requirements, in quantity and quality. Fish have a limited season in which water temperatures allow them to eat, so it is important to understand the value of nutrition to keep your fish happy and healthy.
Neither goldfish nor koi have a true stomach. Unlike other animals that use acid to digest their food, koi and goldfish have long, folded, alkaline intestinal tracts where enzymes and bacteria digest food along the path. At colder temperatures these bacteria work much more slowly, so selecting an appropriate food is vital.
Koi and goldfish require proteins, fats (especially water-insoluble lipids), vitamins, minerals and small amounts of carbohydrates. The right balance will allow for optimal growth, development and maintenance.
The most important times of year to feed pond fish are in the fall, before they become dormant, and in the spring when they become more active. It is vital that fish have a store of fats and proteins to get them through the winter when they’re not eating. It is equally important to replenish those depleted stocks in the spring when your fish are most vulnerable to disease and parasites.
It is useful to think in terms of a base diet and a supplementary diet for your fish. The base diet provides the essential proteins, fats and most vitamins and minerals. The supplementary diet provides additional nutrients and fills in the gaps, but most importantly offers variety. This does not mean different brands of pellets but rather different types of food such as vegetables, insects, pond debris etc.
For the base diet, we recommend a quality commercial food like Aquascape’s Fish Food Pellets. Read labels and be sure the primary source of protein during the cold water season (10°C – 15°C) is derived from vegetable matter, either wheat or soy. Vegetable proteins are easier for fish to digest when their intestinal flora are sluggish from the cold. During the warm water season (15°C+), an animal protein such as krill, shrimp, or fish has the most nutritional value.
The supplementary diet should include algae, insects, decaying plant matter, vegetables (peas, spinach, leaf lettuce, not Iceberg!) and fruit (berries, apple, and pineapple and citrus in limited quantities). If fish refuse fruits and veggies, try boiling them for two minutes or coating them with fish food dust until they develop a taste for the flavours and texture of fresh food.
Koi and goldfish only need to be fed as much as they can eat in three minutes, once daily, as a maximum. This encourages your fish to scavenge debris, insects, and algae from the pond. This is the diet your fish are designed to eat, and it will help keep your pond sparkling clean! If you have water quality issues, reduce feedings to as much as they can eat in three minutes, twice weekly.
Lastly, proper storage of fish food is very important. Food that has been exposed to light or to air will quickly lose its nutritional value and may spoil. If food changes in colour or appearance, or if it contains bugs, it’s better to compost it than run the risk of making your fish sick. Store food in airtight and opaque containers in a cool, dry place. If the water temperature changes before you’ve used up your fish food, it can be stored in a tightly sealed container in the freezer until it’s time to use it again.
Written by our own Fish Specialist, Cass Fortier