The call comes in. One of our customers is on the phone. His fish are acting strangely. Two of them are beating up on a third (poor fish) and he’s had one jump out of the pond. Fortunately it was found in time and survived the ordeal. There’s a strange foam on the water...
What is wrong? What CAN he do!!!?
This is a common and so very natural occurrence. His fish are not ill — they are in love. Goldfish and Koi have very "active" sex lives. To put it in laymen’s terms, the male chases the female in a rather brutal show literally to beat the eggs out of her. Then he fertilizes the eggs. Many times you will notice several males "courting" one female. This can be stressful to the female and can be a cause of injury. Many females jump during this time and injure themselves against rocks or simply jump out of the water and onto the ground.
Mating activity is usually apparent whenever the water heats up rapidly and is more apt to happen in the morning and evening hours. If you wake up to find your pond full of white foam chances are your fish have been "up to no good". The white foam is a by-product of their escapades.
In large lakes fish go into the shallows to mate. The "shallows" in a pond could be your favorite bog plant if the surface of the pot that houses the plant is near the surface of the water. We’ve given our finny pets a "shallows" of their own by filling a lily pot up with large round egg rock and placing it on a shelf. It may be construed as spying but it is entertaining to watch ‘em go!
It becomes dinner (or breakfast) time when the mating ritual ends. Goldfish and Koi are not cannibalistic by nature, however, until a fish recognizes small fry as another fish, the fry is a pretty tasty meal, especially if it is an egg and not yet hatched. All the fish in the pond are treated to "caviar" just after the eggs are laid and they all gather in the "shallows" to grab a tasty morsel.
If you remove the homemade "shallows" and place it in a bucket of declorinated water before the adults have had a chance to pick it clean you may be in for a treat of your own when the eggs hatch in about 7 - 14 days. If the mating grounds go undisturbed and you let nature take its course the fish will eat most of the eggs. Mother Nature controls fish populations this way and somehow, with a little luck, a few babies may survive. It has been our experience that goldfish spawnings are more numerous and yield more naturally surviving young. Goldfish mate and produce young earlier than koi.
Do Goldfish and Koi Interbreed? The answer is yes but the offspring aren’t what you would call show quality. In fact, they are not the prettiest of fish and thank goodness they are sterile.
Unless you are interested in becoming breeders of fish we recommend letting nature take her course. You’ll find that a few babies will survive although odds are against it.