# lava rock as media?



## JohninWI (May 27, 2009)

Hi guys
I just bought a sack of lava rock from the local nursery.  I called the manufacturer and they told me that they don't treat it with any chemicals or dye. 

The lava is about 1/2" to 3/4" in size, and it looks like it's been tumbled to kind of round off the corners. 

what should I do to prepare it for my new hydro system?  The only info I can find on using lava is from aquarium sites and nearly all of the posts say to boil it in plain water prior to use.  I'm not sure why that is--maybe to kill bacteria that could hurt the fish? 

Do you think I would need to boil it? Or give it a good water soak/rinse? Maybe hit it with a little peroxide?

Thanks for any info.


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## zipflip (May 27, 2009)

i was wonderin the same thing. i would think lava rock that size would be best outdoors if it'd be ok to use. but maybe hit some rocks wit  a hammer.  get a bag good bud and burn away and spend an afternoon  hittin lava rocks in ya garage maybe lol.  
  for real tho i am also curious of this.
  as i thought bein it so porous an all an prolly be able to hold hella O2 for roots etc ..


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## purplephazes (May 27, 2009)

If there are methylmercaptains present (smells like sulfer) do not buy them. You will have drastic Ph fluctuations peace and take care !


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## smokingjoe (May 27, 2009)

If Lava rock and scoria are the same thing then go for it.  Treat it no differently to expanded clay balls.  rinse, rinse, rinse, soak and use.

Works very well as an aquarium filtration medium also.


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## Hick (May 27, 2009)

zipflip said:
			
		

> i was wonderin the same thing. i would think lava rock that size would be best outdoors if it'd be ok to use. but maybe hit some rocks wit  a hammer.  get a bag good bud and burn away and spend an afternoon  hittin lava rocks in ya garage maybe lol.
> for real tho i am also curious of this.
> as i thought bein it so porous an all an prolly be able to hold hella O2 for roots etc ..





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## JohninWI (May 27, 2009)

Well, I rinsed and rinsed the rock--it gave off an amazing amount of brick-red stuff!

Anyway, I work as a chemist and today I took some of the rock into the lab and "digested" it and did some tests for sulfur, heavy metals, etc.  Looks good--I put a couple handfuls in a bucket all day and the pH came out to 6.8.  I'm going to run with it.  

I read on another hydro/veggie site that the lava can damage roots if you move the plant around--I believe it!  Mine seems a little friendlier, because I think they must tumble some of the edges off.  Now I just need to figure out how much water it holds so I can noodle around with the pump timer.


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## D3 (May 27, 2009)

Lave rocks have sharp edges. They can cut the roots, thats why grow rocks are smooth. I would not use them.


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## fishcabo (May 29, 2009)

I mix some with hydroton and they seem to work great actually.  I don't understand how they would cut roots.  Is there some little green bud man down in the medium picking them up and slicing them on the roots?


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## D3 (May 29, 2009)

Ha Ha, Lava rock is really glass. It is made from molton rock, put under immense pressure & heat in the center of the earth. It causes the rock to crystallize as it cools creating lava glass, which is lava rock. Lava rock packs tight in your net pots not giving room for movement when needed. Hydroton is designed to move & not pack. As the roots grow & get bigger it will make room by shifting the hydroton where needed. Lava wont shift as well, so it can dammage the roots as they try to grow threw them. Later Man


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## smokingjoe (May 30, 2009)

Personally, whilst not MJ, I have grown in Scoria aka Lava Rock and it works famously.  The only reason you would use that over hydroton is cost, but if that's an issue for you go for it, it will definitely work.

Edit: In previous post I asked "if Scoria and Lava Rock are the same"........  I have since confirmed it is; we just don't refer to it as such in OZ.


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## JohninWI (May 31, 2009)

fishcabo said:
			
		

> I mix some with hydroton and they seem to work great actually. I don't understand how they would cut roots. Is there some little green bud man down in the medium picking them up and slicing them on the roots?


 
I think you're right--I mean, if you pulled rattled the lava around, you'd probably slice the roots up, but they are just sitting there.  It's cool too--i've been able to get a glimpse into some of the root structures as they grow there way through the rock and out of the mesh


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## thekat_420 (May 31, 2009)

I have tried lava rock before.  I stopped using it because the trouble of getting all the roots out of it.  How do you all deal with that?


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## StoneyBud (May 31, 2009)

JohninWI said:
			
		

> Hi guys
> I just bought a sack of lava rock from the local nursery. I called the manufacturer and they told me that they don't treat it with any chemicals or dye.
> 
> The lava is about 1/2" to 3/4" in size, and it looks like it's been tumbled to kind of round off the corners.
> ...


Prior to the invention of Hydroton, I used Lava Rock exclusively. It works great, but as stressed by others, it's not wise to move it. Flexing of the mass of lava will result in thousands of little scissors snipping at your roots...

Just like Hydroton, Lava Rock is porous and holds a great deal of nutrient/water solution between floods in an ebb and flow system. It's what makes it so good for that use.

In DWC I wouldn't think it would matter much. Just about anything with weight and surface for the roots to grab hold to will work. The porosity isn't a concern for the obvious reasons.

I always rinsed my lava rock very well before use to get all the "dust" out of it and the smaller pieces that break off during shipping.

Between uses, I put it into a large metal tub and bring it to a fast boil over a large fire. Stirring it during the boil will remove all the roots. They float to the top and can be skimmed off easily. It also sanitizes the lava or hydroton for it's next use.


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## Adolfo Santos (Oct 15, 2019)

Lava rock works for sure... especially in a drip system if you're worried about over watering and the lava rock soaks up your nutrients and time releases directly into the roots.. They also sell different sized rock if you're worried about damaging the roots. My experience so far, the roots dont get damaged AT ALL. You can buy lava rock online now for cheap and free shipping


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## Daxtell (Jan 1, 2020)

I've been hearing people are using lava in bio buckets hydro in my area.  The porous surfaces provide places for beneficial bacteria to shelter so that they don't allow the bad bacteria to get a foothold.  Anaerobic bacteria has long chains and are the bad bugs.  Aerobic bacteria are the little rods.  (I may have to get a microscope.)

As if an omen, I caught my air stones not working again.  This is the third time in my first grow.  I am changing/adding a water fall aeration for my upcoming grow and seeing if growing can be less adventuresome.

I've tried the cheaper air bubblers and the pourous (neoprene?) bubblers.  I've up sized my air pump to overkill according to the math.  I need a better airstone.  Changing/cleaning every few days is not that common, but it's my solution until I get the cause sorted out.

Hydro has me hooked on growing.  When problems crop up, they hit fast, but changing whatever is wrong seems to let the plants get right back on track immediately.


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