Beach Rocks

[TheFishEnthusiast]

I'm looking to get some rocks from the beach tomorrow. I plan to add them into my tropical fish tank. Once I get them home, I will be boiling them for 24 hours or so. Is it safe to add these rocks? It's mainly to add hiding places for my fishes/bristlenose plec. Pet shops charge like £10 for a few rocks and it's really not worth that amount when I have a beach so close.
 
Thoughts?

 

[Ninjouzata]

Not sure if it'd be illegal or not to take them..but you certainly don't want to boil them as they could explode.
 
I believe you can pour vinegar or something on them and if they fizz then it means they can alter things like the hardness or pH of your water and you wouldn't want to use them.
If they don't fizz they're safe but you still would want to scrub them well and soak them.

 

[Byron]

Agree with Ninjouzala.
 
The acid test is to determine the calcareousness of the rock.  Vinegar may do it, but a stronger acid is better; the Regent #2 in the API nitrate test kit is an acid.  A drop or two on the rock, and if it bubbles or fizzes you know it is composed of calcareous mineral and this will dissolve into the water raising the hardness and possibly pH.  This wouldn't likely matter much in a hard water fish tank but in soft water fish tanks this could be a problem.
 
One further issue is what the rocks may have absorbed.  There is no way to know this, but substances can leech out regardless of how well you scrub them.  Salt if the beach is ocean would be my main concern with this.
 
I have had good luck with river rock purchased from landscape and rock suppliers.  These are very inexpensive, 75 cents for a large pail of various sized rocks and pebbles.
 
Byron.