# info on lava rock for sub



## wicca27 (Oct 13, 2008)

i am thinking about using lava rock from the home improvement place. i was thinking about puting it under my normal natural gravel to help. will it help the plants any or just promote better bacteria? also will it "melt" over time where i have to replace it? how much rincing do i need to do to it? any one have pros or cons to share. thanks every one


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## Dryn (Sep 6, 2007)

The key to a good substrate is one that not only adds nutrients to your tank but also is able to absorb and retain new nutrients (CEC). As far as I know, most lava rock is completely inert, meaning that it doesn't have any nutrients. However, it is very porous and could provide a great place for various microorganisms that are essential in nutrient exportation. The rock itself doesn't have a very high CEC as far as I know. I've used it extensively in outdoor pond filters as the biofilter and it works great that way. It probably wouldn't make a very good substrate in a tank though. Vermiculite would be a much better substitute. It is very cheap, has a high CEC, and provides many nutrients on its own. You would need to soak it very well and mix it with something to keep it from breaking down and compacting though. I hope this helps.


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## bradac56 (May 9, 2007)

Vermiculite is just another old school fired clay inert product so all it's adding to your tank is trace iron.

Examples of other inert clay substrates: Eco-Complete, Fluorite, SMS/Turface, SAS, pool filter sand.

Examples of non-inert substrates are AquaSoil and MS.

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Even AquaSoil and MS runs out of nutrients after awhile so depending on your lighting and C02 you'll need some type of fert regiment.

- Brad


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