Lava Rocks?

[VinceC_69]

My friend is getting rid of his old tank equipment and is giving his stuff to me he said he has some lava rocks for me as well. What are they exactly? obviously from the name i figure there lava from a volcano lol but do they effect PH or water parameters in any way? any info would be great thanks all

 

[tcarswell]

I have them its the red chips of rock you sometimes see in peoples house fronts but bigger. I like them as they are porous easy to modify and they do provide some biological filtration. (from being porous they have a large surface area.

 

[tcarswell]

See the rocks on the right hand side?