transferring protocorms in liquid medium

[King_of_orchid_growing:)]

I have a flask of seeds that germinated some time during late August to early September.

The protocorms are in liquid media. They're still very, very tiny. You need a jeweler's loupe to see them and still not too much bigger than the tiny seeds.

These guys are growing steadily, but they're slow growing at the moment.

How do you know when to replate?

How would you do such a thing when they're just gonna float around in the media?