i had breed flower horn and some guppies before. i fed them the boild egg yolk.
But i'm not sure if it's suitable for pencil fish fry.

Anyway will just tell you the way to make it so you can try if you want.

First thing, cook a hard boild egg. let the egg cool down and take out the egg yolk, the white portion...feed it to yourself...hehe

Secondly, scrap a small portion of egg yolk out(quater or half, depending how much you want), get a small container, bottle or whatever(water tight) that is as small as a 500ml coke bottle or smaller(smaller the better). Fill in some clean water(preferly cooked), chunck the small portion of egg yolk and put it into the bottle. The rest keep it in the fridge or just feed it to yourself again.

Finally, cap the bottle or container, and give it a good hoolaa shake.
The end product is yellowish liquid with very very very tiny egg yolk.
Feed a very little bit to the fry, feed them as much as they can eat. But you have to make sure you water is in good condition at all time. change small amount of water regularly(10%-30%)

Good luck