What is this?!

[lilsd]

Setting up to cycle a new planted tank, and I found this inside the rock wool in one of my
Anubias. Wtf is it?!?! Eggs? Fertilizer?

 

[MattW]

To me it’s fertiliser. I have never come across plant sellers doing this before

 

[GaryE]

I'd take one out, and try to crush it, to see what happens. That should tell you if it's an egg. It's not something I've seen before, but I have bought plants with gravel caught in roots (that looks too manufactured) and with unwanted snail eggs.

 

[Boundava]

Fertilizer.