Marble and Granite Rocks, Safe for Fish?

[Acro]

There is a Marble and Granite supplier near me, that puts their broken pieces out on the side of the road. The broken bits are free for the taking! Some pieces are rather large too and normally meant for counter tops.

I'm setting up 2 stock-tank ponds and I'd like to create levels and caves for the fish. As long as the pieces are secured and have no sharp edges, would Marble and/or Granite be safe for fish?

 

[Ogertron3000]

I think so, try the acid/vinegar test. Drip some on and if it fizzes it's not safe.
Do you know if the marble is treated with anything if they intend to use it for counter tops? Might be something to check first, maybe you can just ask them, I'm sure they'd would be happy to answer if it means you are going to take away and make use of their rubbish for them.

 

[FJB]

Granite will be chemically inert in a freshwater tank. Marble (originally a carbonate), will dissolve slowly in water that is neutral or below. As suggested, the acid test will demostrate this.

 

[kno4te]

May increase ur water hardness but do what the others have mentioned for testing.

 

[Acro]

Sounds great, thanks to the three of you!

 

[Lepisosteus]

Depends on the type of system you are going for. I would bet that marble, even limestone would not have a terribly noticeable effect on most tanks if the rocks are collected in a similar area from where your tap water originated.

 

[TwoHedWlf]

Like above, both should be fine, marble will slightly increase your hardness and PH, but unless you've got a lot of it or are trying for a very low PH, it's likely to be negligible. I throw a bunch of coral fingers into my filters specifically to increase the PH in my SA Cichlid tank(I don't know why I call it that, only 2 out of 10 are SA cichlids.)

 

[FINWIN]

I've had marble, granite, onyx and quartz spheres in my tanks with no problems.

No sandstone, limestone or anything with ferrous (iron) veins. No mica or graphite.