koi fry

Question
I have (had) 200 koi in a tub outside to seperate them from the older fish in my pond. Their numbers are declining daily. I have checked water quality. I believe insects or some predator is eating them. When is it safe to move them to my indoor aquarium? They are 8-10mm (1/4") in length. They are 10 days old now.

Answer
As you probably know, the mortality rate for koi hatchlings is pretty high, so they may be just dying.

They can go into an aquarium any time, but you need to make sure that they will not be sucked into filters and such. Also make sure they have adequate food. Once the egg sack is gone they need regular nutrition to survive. Tiny bits of squished hardboiled egg yolk will do when they are very small.