Cool clip!
I'm not sure what you mean buy water change in the fry tank.
I use water from my main tank for my fry tank. I set it up 1-2 days before the hatch night and add more main tank water as I catch the fry in a cup to thier tank. After they are in the tank I think most people do a 20% water change daily. I don't I just do one in a week or so. For me its trial and error. I'm not so good at water changes I suck up alot of fry.

You don't have to hatch brine shrimp until your fry are about 5 days old.