Lava rocks

[Rhinohorn420]

I wanted to know if lava rocks can be used in a sump. Instead of going out and getting rock from the lfs

 

[wkscott]

Probably not a good idea in a marine tank. Most of these rocks are silica-based and this will cause a huge diatom problem in your tank. Many also contain metals such as iron and this will fuel green alga outbreaks and too much iron is deadly to your creatures.
https://www.google.com/search?q=lav...oid-sprint-us&sourceid=chrome-mobile&ie=UTF-8

 

[cromag27]

I would not recommend it. you have no idea what was in the soil it came from.