Volcanic Rock

[J4MES]

J4MES

 

[The-Wolf]

see my sig and click the link for rocks

 

[J4MES]

so it's safe then?

J4MES

 

[*Fishkies*]

Volcanic Rock/Lava/ Scoria.
Photo used with permission from Franklin Institute Science Museum and Tammy Payton www.tammypayton.net
Scoria is completely inert & very light. It needs to be mixed with rounded stones because it is too jagged for fish to use for spawning. It has an unnatural looking purple colour when new, but it soon naturalises. Scoria rocks are igneous rocks which were formed when lava cooled quickly above ground. You can see where little pockets of air had been. Scoria is actually a kind of glass and not a mixture of minerals.
Note; do not boil or roast due to possible explosions of trapped air pockets.

Volcanic Rock information

The above link is where the information is from.

I would say it looks to be okay to use. (I'm not a professional on this, just my thought) It doesn't specify that it should not be used at all.