What kind of rocks are these?

[mattmathis]

Anyone have much experience with rocks? I have some that I have had laying around the house and would like to put in my aquarium. Has anyone tried anything resembling these in their aquarium?

All comments welcome!!!

Rock 1)

Rock 2)

Rock 3)

Rock 4)

 

[Dano01]

I could guess that the top two flat rocks may be a granite or a sedimentary type of rock...The semi football shaped rock may be a granite river rock.....The three cheese colored rocks look like they may be lime stone.........??? on the red ones.

Put strong vinegar on all of them and look for "fizzing". Fizzing or foaming would indicate calcium and rocks with calcium are not good in a general aquarium environment.

 

[jsoong]

The top 2 are slate, I think. The middle ones might be carbonaceous. The red one, ????, but usu. red indicates presence of Iron.

Slate would be safe for aquarium. To be sure, test with a bit of vinegar & see if it bubbles. If it does, it isn't slate & will dissolve into soft water. Main problem with using Carbonaceous rocks (ie CaCO3) is that the carbonates will dissolve into water (the calcium is not that much problem). Carbonate will increase your KH & pH.

If you have hard water, this is not really a problem. When your pH is 8, the water is basically saturated with carbonates so any additional rock won't make any difference. If your water pH is in the 6's, the rocks will really mess with your water parameters.

If the rocks pass the vinegar test, it would be wise to soak them in a bucket of tap water for a couple weeks. Measure your KH & pH before & after. If there is no change, the rocks should be fine.

<BTW, Iron containing rocks are best left out of your tanks - they stain silicone & glass, and might promote algae.>