How can I tell if a rock is freshwater safe?

[Orca]

Can anyone give me some tips on how to tell if a rock is safe for my tank?

I found some really cools rocks on a beach in Mexico. I'm pretty sure they are slate (flat, smooth, and black), and I think they'll look great with the black substrate in my community tank.

Is there a way I can determine that they're safe for the tank? I read somewhere that you can test rocks by putting a weak acid on them (such as vinegar), and if the acid doesn't bubble, it's safe. :?

TIA

 

[Endgame319]

Not a weak acid, a strong acid like muriatic acid, vinegar just doesnt cut it. And soak it in a bleach solution (not sure on proportions) to kill off any bad bacteria.

 

[Allivymar]

*nods and agrees with Endgame*

You can try vinegar; if it bubbles then you know you don't want the rock in your tank (it will mess up your water hardness/ph). Thing is, vinegar is a pretty weak acid, so it if DOESN'T bubble, theres no guarantee the rock won't mess things up; the vinegar may have just been too weak to cause a reaction.

 

[millipede]

rocks...

I never heard anything about it but it makes sense to me... certain types of rock that would affect water parameters would probably bubble with vinegar on it. I remember once I was cleaning some shells from the beach with vinegar and it was just eating it up. So rocks high in calcium or something would react in that way. However smooth black rocks sound fine to me. If they were on a beach I'd be willing to bet they are clean enough to just rinse and put in... obviously others would disagree... I wouldn't use anything like bleach... I'd either just rinse real well in hot water or maybe even boil them if you just wanted to be safe... smooth black rocks, unless they were involved in a chemical spill or something, shoulnd't have any ill effects on a tank... I say your safe but you may want to read a few opinions before you decide...

 

[Allivymar]

Wheee! Simulpost with millipede *grin*

 

[millipede]

I would have beat you if my internet wasn't so slow...

 

[Allivymar]

Oooo! I saw that! millipede offered to beat me; I'm telling my husband

I would boil/bleach the rocks btw; forgot to add that. Never know what they were laying in.

 

[Menagerie]

I will add that I picked up some river rocks. My fiance did all the work as far as bleaching (very little--2 gals of water to 4 TBSP of bleach) them and rinsing, rinsing, rinsing. The rocks are in the tank and they look great and are giving the brichardi something to swim around!

 

[Orca]

Thanks for the advice everyone. I've already boiled the rocks, and I'm pretty sure they're safe, but I'll do the muriatic acid test just to be sure.

 

[madasafish]

Well, I'll just say that there's really no guarantee on the safety of rocks found in nature... A NJ DEP biologist I recently spoke to said that his drinking water was contaminated by a layer of relatively-porous slate (or shale, I've forgotten) with arsenic imbedded in it. You never know...