How big do the koi have to be to lay eggs?

I have 4 koi 12 to 16 inch long and 4 that are 5 to 6 inch. About a month or so ago we had babies and they are about an 1 & 1/2 inches long. There are probably 75 to a 100 of them in the pond. This weekend I cleaned out the settling tank and moved some babies into the pond that were stuck in the tank. Two of the fish that I moved are 2 inch and have big bellies as if they were ready to lay eggs and I'm not sure that is possible. Maybe they are just really healthy like some of us Also in the settling tank are a few, half inch long new hatchlings and I don't know where they came from as I haven't noticed any big bellies on the larger fish. Any ideas?

Koi will typically need to be 10" to 14" to lay eggs. Now that is small for a female to lay eggs but I have seen it happen. Usually the female will be in her second to third year if they are laying eggs so consider them mature if you will.

The baby koi with the big bellies may have some internal problems. Remember koi will lay thousands of eggs so not all of them are meant to be reared. Nature has a way of natural selection. In fact the big bellied koi somehow were sucked into the bottom drain circuit, right? In the wild they would have been "toast". That's my thought.

It's great to hear your fish have spawned!

The Pond Digger

So the eggs came from one of the 4 larger fish more than likley. What is the window that the eggs will hatch. Could the new couple of new hatches be from the same egg lay, as most of them hatched out about a month ago?

To the best of my knowledge without looking anything up formally the eggs will be little fry swimming around in two weeks give or take a few days.

The breeders in Japan are doing their first cull on Shiro Utsuri at 50 days and again at 70 days. If that gives you any idea of how fast the fish are developing in the first couple months.

Is it a possibility the two little fry are runts from the same brood?

The Pond Digger

Thanks for the info.

The babies are amazing to watch grow and their colors are showing more all the time. I enjoy spending time in the back yard feeding and watching the fish. We are very happy with the new pond.

The other day I had string algae building up on the rocks of the waterfall and put some of the pond scrubber from PD and it works wonders. Its an amazing product. Thanks