Crumbly Rock A Problem?

[CrazyDiamond88]

I bought a really nice rock yesterday from my LFS, it is called Honeycomb Nano, brand is  Pisces. 
 
Thing is, it seems to be quite crumbly, and when I rub my finger on it, yellow from the rock gets on my finger.
 
Will this be a problem?
 
Is there a way to stop it?
 
I tried the vinegar test also and it didn't fizz.

 

[paradiddle]

Soak it for a few days in old tank water, test the water before you put it in and after a few days, test for everything to be sure, ammonia nitrite nitrate, gH, kH, pH etc
 
If it crumbles or discolours the water but doesnt affect the levels, you could add it and use carbon to remove the colour from the water, but is it worth the risk and expense?
 
As nice as it may look, its not worth the money youve spent on your tank to ruin it with a rock 

 

[Tongue_Flicker]

Or you could put that rock in another temporary tank and grow some plants & algae on it til roots can anchor the rock securely in place then adding it in