I am currently hatching them with a 1 liter Mt Dew bottle. I cut out the bottom of the bottle and put it top down in a jar. I fill it to about 2 inches from the top with 1 table spoon of koser salt (dill salt?) and put an airstone all the way to the bottom of the bottle which should be the top if you know what I mean

I run it for about 15 minutes so the salt is all one and the water is clear. I then put in a smal (tiny) amount of eggs so it's only enough to feed them for a day or 2 at most. I have about 50 betta fry so they don't really eat much plus I am feeding them microworms. BBS are good for up to about 24 hours after they hatch at most. After that, all their egg yolk has been absorbed and the bbs are mostly shell which not as nutritious for the fry. To harvest, as note in previous posts, just pull out the airstone and let the water settle for about 5 minutes. The bbs will gather to the brightest area of the bottle. I use small dropper to pick them up and run them through a small net right on top of the bottle. I use a baby food jar to get some water from the fry tank, run my net of drained bbs in it and then pour it evenly to the fry tank

A sloppy job but is working OK so far. My first batch of bbs, I put too much eggs in there so a lot was wasted. Test it out and eventually you will know exactly how much your fry eats and use only enough bbs eggs per batch.