Tagging/Marking frag plugs?

[TechGuy]

Anyone tag or mark their frag plugs? I want to number each plug so I can measure/track its growth and placement in the tank.

This way I can know when it was fragged, from what colony, track its health/growth in reference to placement/tank parameters at a specific date and time.

Anyone think a sharpie might work? Or is toxic when dry?

[lazylivin]

When I purchase frags from http://www.atlantisaquarium.net they come on frag plugs where the name of the coral is written on the stem with a sharpie. So I think that would be fine.

[coral ranch]

alot of ours are marked on the botto with a sharpie