As for the egg yoke, there are even some commercially produced foods with a lot of egg in them. Ken's Foods has an egg flake. (Click the link on the GL Homepage.) The freshly hatched bbs (baby brine shrimp) or the decapsulated bs are even better, usually, than the egg yoke based stuff.

I wouldn't both with powdered chicken egg yoke in your fry tank though. I know that it has been useful, but there are so many "cleaner" foods available. Why have a cloudy tank, need zillions of pond snails on clean-up patrol and have to do partial water changes very frequently, like every time the tank clouds from uneaten powdered egg yoke - if you don't have to? :)

Having said that, next summer, because I’m cheap and curious and perhaps an idiot, I may powder the yolk of a hard boiled egg to sprinkle very lightly on the surface of a Daphnia culture outside. In fact, I'll bet there is a restaurant supply place which sells powdered egg yoke. (The yoke's on me.) If I overfeed and suffocate that culture, we will re-start it (from another) and use good old green water to suppliment the leave which fall in. ;)

The question of live food cultures is a whole 'nother line of inquiry. There are so many excellent food cultures, yet most aquarists need never bother with the cultures.

On a historical note, when aquarists (in large numbers) powdered egg yokes, it was because they didn't have brine shrimp and brine shrimp eggs (first used by aquarists around San Francisco Bay) or many other prepared food. Perhaps the only flake available was made of rice. Since, except for goldfish, most aquarium fish can't utilize much starch, that flake produced a lot of roughage and little nutrition. People did go to forest preserves and country ponds to collect live foods A.) because those ponds were there then and B.) because they had to. ;)

A couple of cautions on dividers. A lot of fish are amazingly adept at jumping over them. I have used them. They also can allow one to over crowd a tank, because we have enough guppies (or whomever) in either side to over tax that aquarium. :)