May I feed the fish in the Administration Building pool?

The colorful koi—or Japanese carp—that live in the pool surrounding the Arboretum’s Administration Building love to be fed! Our challenge is to make sure that they eat only the special food that we purchase for them and that they don’t eat too much of it. On most weekends, visitors will find this special food in dispensers on the terrace at the southeast corner of the pool. We charge 50 cents (quarters only) for a handful in order to help defray the costs of caring for the fish. We cannot keep food in the dispensers all week long as it results in over feeding the fish, which is bad for them. Feeding the fish any other type of food also causes problems, so we ask visitors to refrain from offering human food to the fish at any time.

Koi always look hungry when people approach the edge of the pool, but you needn’t feel sorry for them. We treat our koi better than they would be treated if they were in the wild. Koi are naturally gluttonous and are opportunistic feeders, but in a controlled environment we must regulate their intake of food to keep both the fish and their environment healthy. Over feeding the koi causes excessive amounts of fish waste, which contributes to more algae in the pool. To keep the algae down, we use barley straw extract which inhibits algae growth naturally. We also dye the water black using a nontoxic dye to keep the algae from growing excessively; a secondary benefit is that it gives the water a reflective look.

Visitors play an important role in helping us keep the fish healthy. When they do not feed them human food and do not touch them the fish thrive. Even though the fish look “petable,” touching them removes a natural slime layer, which they need as a natural barrier against disease. This layer serves as a sort of second skin.