a type of rock called flagstone

[baddfish]

Does anyone know if this can cause damage to either fish or the water quality of the tank?

 

[Paullywolly]

Check with some vinegar or HCl to see if it reacts. I think flagstone - if it's the kind you use for landscaping - is a shale-like sedimentary rock and should be fine, won't increase water hardness.

 

[guppy]

Flagstone is the shape not the type of rock, avoid the reddish brown types as they are high in iron content, Pennsylvania bluestone is excellent for tanks and ponds as is rocky mountain gold quartzite.

 

[brianp]

Get a chunk of the proposed rock and place into a 1 gallon container. Allow it to sit there for a few days. Purchase a feeder goldfish and add it to the container. If the goldfish is still alive 24 hours later, the rock is probably aquarium safe. This is the only reliable way to test, given the wide range of toxic substances which could be present. Use a fairly good size chunk of rock so that the limited, 1 gallon volume will concentrate whatever may be leaching from the rock.

 

[scubasteve06]

Yes be careful...I remember a member on here using some flagstone rock from Home Depot and it killed some very big very nice fish...