Still may be a problem then eventually with the size of pond, one thing I do know is there were no new plants or anything put in the holding pond other than the koi and the one goldfish for over 12 months whilst the bigger pond was being built so they must be hybrids that is the only other logical explanation.
I am thinking of getting an air stone and compressor to increase the amount of small molecule air in the pond, I already have a large waterfall shifting about 1000 litres of water every few minutes which has sufficed, the agitation at the base of the waterfall is quite aggressive and the koi love hovering under it I have about 7 large koi now between 24? and 30?.
Obviously I would like to make their life as great as possible and I heard especially in deep ponds that an air stone is an asset and improves air efficiency to the lower parts of the pond is this true and what would you recommend? The pond is over 4 foot deep with a 2 foot shelf on one side.
Thanks for your help.
Fishlady wrote: Two possibilities: the young are goldfish/koi hybrids (most likely as goldfish and koi interbreed very easily) or alternatively if you added any plants to the pond that came from a stocked pond elsewhere it's possible that there were fertile goldfish eggs on them. 99.9% likely that this is just a simple goldfish/koi spawning and the babies are hybrids.
Common goldfish can reach 18 inches/10lbs in the right environment. Koi/Goldfish hybrids anywhere up to the max for a pure Koi.