Need advice on invasive something...

[Frogger]

Wouldn't recommend ever boiling your rock. Too many people have ended up in the hospital doing that.

Colonial hydroids are no big deal. Their sting doesn't seem to harm any of my corals. And they eventually get knocked back by active healthy coral growth.

I have had them in my tank for 20+ years and they never amounted to much. I can still find them if I look hard enough.

If you really want to get rid of them and you have tons of time and patience on hand you can bleach your rocks followed by a Muriatic acid bath (outside only) and you can start fresh with completely dead rock. However you will have to recycle your tank and likely go through the ugly phases for the next few months.

Any time you buy a coral with a bit of rock, a bit of exposed dead skeleton, plug or a snail, hermit crab you risk adding a nasty.

There are many many nasties that are way worse then hydroids. I would reserve my fight for something far worse.