If you have fish in your pond, sooner or later they are going to have babies. Late spring to early summer usually marks the time of year when koi and goldfish start to spawn. When koi and goldfish spawn, they produce thousands of eggs but very few actually survive and grow up into baby fish. Koi are egg “scatterers,” meaning they generally deposit their eggs on the bottom of the pond or in plants.
The eggs hatch a few days after although you probably won’t be able to see them for several weeks because they are too small. At this stage in development, the babies will feed off of all sorts of microorganisms in your pond. After a couple months the babies are about an inch long and may start eating commercial food. In order to “bulk” them up, look for a food that has high protein content. Depending on the pellet size, it may be necessary to crush them in order for the babies to eat the food.
By the end of summer you’ll have to decide whether to bring the babies inside or let them over-winter in the pond. If you decide to let them over-winter outside, they may or may not survive because they don’t have enough fat reserve to tide them over. If you decide to bring them in, make sure you have a large enough tank with adequate filtration because they will continue to grow inside.
Another thing to remember is that if your pond babies continue to survive year after year, sooner or later they are going to get big and could overcrowd your pond. If you plan on keeping some of the babies, understand that eventually you may have to get rid of (cull) some of them. Watching the baby fish grow up is fun and the whole process is a great learning experience for kids and adults, alike.