if you knew who the parents were you could start culling them. but I'm not sure what are key features for ones that will have bad colouring and ones that will have good ones. For that you'd have to wait till their atleast 4 months old to be sure about it but the japanese basically start culling when they are born. Besides from that you could start seperating them to ensure that you get the most out of this spawn ie) seperating the larger ones from the smaller ones.

My first set of spawn, there was only one that had good colouring (which was 2 months ago) so I sold/got rid of the others and kept them. My new spawn, is still too hard to tell cause they are just three days old but are starting to show colour.

and a quick question what are you feeding your kois?

So far they seem happy eating the algae. I have not put too much thought into it. I have had some of these kois for over 15 years, and this is the first time I've had any activity.

according to my grandfather if you feed them egg yoke they would grow faster, which is what I'm feedin mine, but they are also eating algae. but yours right now could start eating mosquito larvae, if you have any buckets of water lying around with squirming worm like things you can feed them those.