KOI / GOLDFISH SPAWNING
Koi and goldfish can and will spawn in your pond when the time and elements are right.
Female and male fish are generally difficult to tell apart. Females are normally larger with substantial girth to them. Make no mistake when the spawning months come around in the early to mid part of the year -the females will have a swollen underside.
The girth of the fish will give away its female identity. This swollen belly is due to hundreds of eggs waiting to be expelled. When the fish spawn, you will see several of the thinner males chasing the female(s) all over the pond bumping and nudging their sides and stomach area.
The fertilized eggs are thrust into a very dangerous world mostly at the mouth of their cannibalistic parents!
If you don't want fry of the koi or goldfish - leaving them be will minimize any making it to adulthood. There will be fry that make it, but numbers will be kept in check, especially by removing all the eggs you find or the introduction of GAMBUSIA minnows that will turn on the small fry in replace of mosquito larva.
If your intentions are to insure the largest surviving percentage of fry,
immediately take out the eggs so neither they nor the fry that will emerge in
the days to come are eaten by hungry pond mates.
If you don’t have underwater plant matter for the fish to lay the eggs on, use a brand new, NO CHEMICALS ADDED mop head to serve as a wonderful substitute for the eggs to stick to. It’s much cleaner and easier to move as well once the eggs have been deposited. There are also manufactured spawning ropes and brushes that serve the same purpose.
Keep the eggs in clean, oxygenated water. Remove any eggs that have a MILKY solid look to them as they are INFERTILE and as they decompose can effect water conditions and cause a water mold to spread to good eggs.
Once the tiny fry emerge they feed for days on the small egg yolk attached to them as substance. You will often find some of the fry grow larger and faster than others. These fry are called “TOBIES”. They will often eat their smaller siblings for food!
Check out the picture below– you can see a small fry in the stomach of a TOBY!
KOI INTERBREED WITH COMETS / GOLDFISH?
It often happens that koi interbreed with other species of goldfish.
Those peculiar fish you might find in your pond may be a indication that your fish are mixing.
Often called MULES- these fish often don't have the beautiful coloration of either parents and often have odd body shapes.