# Lava Rock with clay as substrate base layer



## jellopuddinpop (Dec 12, 2016)

Hi everyone,

I’m working on putting together all of the pieces of my new build, and have a substrate question. I’m going to be setting up a 125G tank, and want to have a little height to the substrate near the back. ADA Powersand is just too expensive for my needs, so I’m thinking about using crushed lava rock in its place. My question is: Can I mix some clay into the lava rock for the high CEC and the iron content, or will that defeat the purpose of the lava rock (in preventing compaction of the substrate).


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## Axelrodi202 (Jul 29, 2008)

In my latest tank I used crushed lava rock as a base for some of the tank because I couldn't procure enough power sand in time. It's worked well so far, though with the time I spent washing the stuff I was wishing I'd been able to just use power sand. 

I'd think clay would lead to compaction issues. Lava rock already has CEC (in some tests I did the TDS of a cup of water in lava rock with it actually decreased after a few days). I don't know about iron content but I'd assume based on the color it has some iron oxide or something similar. 

FYI, the primary function of power sand (pumice-based) is to provide surface area for bacteria to grow in the substrate.


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## jellopuddinpop (Dec 12, 2016)

Axelrodi202 said:


> In my latest tank I used crushed lava rock as a base for some of the tank because I couldn't procure enough power sand in time. It's worked well so far, though with the time I spent washing the stuff I was wishing I'd been able to just use power sand.
> 
> I'd think clay would lead to compaction issues. Lava rock already has CEC (in some tests I did the TDS of a cup of water in lava rock with it actually decreased after a few days). I don't know about iron content but I'd assume based on the color it has some iron oxide or something similar.
> 
> FYI, the primary function of power sand (pumice-based) is to provide surface area for bacteria to grow in the substrate.


Thank you for the help! I was under the impression that the Purpose of powersand was to help keep the deeper areas of the substrate from compacting and causing anaerobic pockets. This helps!


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## Axelrodi202 (Jul 29, 2008)

You're welcome. This link discusses the ADA substrate system in detail.


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## jellopuddinpop (Dec 12, 2016)

Axelrodi202 said:


> You're welcome. This link discusses the ADA substrate system in detail.


Thanks again!


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## milesm (Apr 4, 2006)

check out this vid: https://www.youtube.com/watch?v=nHvFXNiVfIA

i don't know how to make "this" or "here" to reference a ink. does one need special software to do so?


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