[Sasami]

I would move them...maybe consider splitting the group in half . Crowding young, growing fish fry together actually slows down (or even halts) the growth for most of the fish.

As for how long they take to grow, I'm not sure. It depends so much on water quality, size of the tank, genetics, diet, etc.

 

[Sasami]

Ok, thanks! So a group of 12 and 13 are ok? I thought that would make the groups a tad small. I was thinking more like 15 and 10, but I can do half and half!

10 and 15 is fine, I just meant to split the group, it doesn't have to be exact .