# Is lava rock safe for use under the substrate?



## Zak Rafik

Hi everyone,
I'm in midst of setting up my new planted tank and intend to use lava rocks (2 - 3 cm) under the substrate.

The are two main reasons I'm doing this way.
1. To reduce the number of ADA aquasoil I need to buy when creating a slope at the back of the tank and also to give a bit of overall volume to the tank.

2. To avoid using ADA power sand special  which is very costly

I still have 3/4 full bottles of ADA Bacter 100 and ADA Clear Super each, left over from my last scape. I intent to lay the lava rock and then apply Bacter 100 and Clear Super on top it. Following this, I intend to have 2 inch / 5 cm of ADA aquasoil.

I'm reading some rather conflicting information on the use of lava rock as a base for a planted tank. Some strongly advocate it for it's  ability to create an  anaerobic environment inside the rock for beneficial nitrifying bacteria. . That it is an inert stone which does not change water parameter.
And then, there are some that say it can lead to buildup of toxic gas and not really that useful in a planted tank There are even some that say and I quote "Lava rock contains some hard metals that can leak out and be dangerous to your tank".

Now my questions are:
So what is the real picture on this? 
Is lava rock as beneficial or not beneficial or meh (nothing)
It will be helpful if the fellow members can shed some truth on this matter. 

Thankx in advance for sharing your experiences and opinions.
Cheers.




IMG_4880 by Zak Rafik, on Flickr


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## Cor

I've seen that Amano used it in his tanks, so I'll guess it wouldn't harm.
It's good for circulation beneath the soil and it's good for the bacterial development. Much cheaper as powersand do.


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## MatusG

I agree that you can use it under soil to not spend it so much. Its good to put it inside bag in case you would like to remove it after some time when rescaping. Much easier to work with after 


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## dw1305

Hi all, 
I think it should be fine.

cheers Darrel


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## Zak Rafik

Cor said:


> I've seen that Amano used it in his tanks, so I'll guess it wouldn't harm.
> It's good for circulation beneath the soil and it's good for the bacterial development. Much cheaper as powersand do.


Hi Cor,
Yes I have read that Master Amano uses them but not for use under the substrate.
For the price 1 bag of PowerSand, I can buy 30 kgs of lava rocks.



MatusG said:


> I agree that you can use it under soil to not spend it so much. Its good to put it inside bag in case you would like to remove it after some time when rescaping. Much easier to work with after


Thanks for the tip MatusG. That's what I'm intending to do. In fact I'm already collecting those mesh bags used to pack oranges and use them to stuff the lava rocks. Save some $$ and get healthy at the same time.


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## Zak Rafik

dw1305 said:


> Hi all,
> I think it should be fine.
> 
> cheers Darrel


Hi Darrel,
I've bought some 10+ kg from a LFS last week.
Since you're very knowledgeable with chemistry stuff, can you tell me if lava rock contain any sort of beneficial minerals in them.
If red lava rock is formed when the lava stream flows and cools down with the air remains and becomes small holes in the final red lave rock, how is it that this stone is stated as inert.
Shouldn't they contain iron ( as seen by the reddish colour of the stone) and other minerals? I have always been curious about this.
Cheers.



Lava rocks by Zak Rafik, on Flickr



Lava rocks-2 by Zak Rafik, on Flickr


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## Nelson

Just the same as JBL Volcano mineral.
George uses it a lot now .


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## dw1305

Hi all, 





Zak Rafik said:


> Since you're very knowledgeable with chemistry stuff, can you tell me if lava rock contain any sort of beneficial minerals in them.
> If red lava rock is formed when the lava stream flows and cools down with the air remains and becomes small holes in the final red lave rock, how is it that this stone is stated as inert.
> Shouldn't they contain iron ( as seen by the reddish colour of the stone) and other minerals? I have always been curious about this.


It definitely will contain some available nutrients, how much will depend on the volcano and how vitrified the rock is. 

I think these rock are formed from basic basaltic (shield) volcanoes, so are technically are <"Scoria">. 

cheers Darrel


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## Zak Rafik

Nelson said:


> Just the same as JBL Volcano mineral.
> George uses it a lot now .



Great! I think I should have no problem with my intended plan. 
Thanks


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## Andrew Butler

Zak Rafik said:


> I'm in midst of setting up my new planted tank and intend to use lava rocks (2 - 3 cm) under the substrate


How did you get on with using the lava rocks? I'm looking at it also to bulk out the aqua soil and make it a little more sturdy - a little like powersand.



Nelson said:


> Just the same as JBL Volcano mineral.
> George uses it a lot now


If you're one of the people that intends to reuse their aquasoil then don't use this stuff as you will never separate it from the soil; there are lots of very small pieces in the JBL volcano mineral.


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## Nigel95

Andrew Butler said:


> If you're one of the people that intends to reuse their aquasoil then don't use this stuff as you will never separate it from the soil;



Could put some lava split in filterbag to keep it seperate from aqua soil.


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## Andrew Butler

Nigel95 said:


> Could put some lava split in filterbag to keep it seperate from aqua soil.


This was only the jbl volcano mineral but some pieces are really tiny so would need a very small mesh.


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## paul_j

I used pantyhose


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## AverageWhiteBloke

paul_j said:


> I used pantyhose



Good of you to share Paul, must be liberating. What about the volcanic rock though


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## ceg4048

Zak Rafik said:


> Now my questions are:
> So what is the real picture on this?
> Is lava rock as beneficial or not beneficial or meh (nothing)


The real picture is this:
Lava stones/gravel is no big deal. It will will neither be a factor in failure, nor in success. There are very small levels of micronutrients in the rock, primarily Ferric Iron, which can be passed on to the plant roots, but so what? Even the detritus from accumulate fish and plant waste will produce more varied and high quality nutrition for plant roots than the puny amounts of micronutrients in the rock. The material itself has good CEC, so this is fine. There is certainly nothing to fear, but also nothing to write home about either.

Cheers,


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## Costa

I understand that lava rock is a great filter medium too.


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## ceg4048

Yeah, well, so are chopped up scrubbies, which are cheaper and offer less drag.

Cheers,


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## Andrew Butler

ceg4048 said:


> so are chopped up scrubbies


You do like your chopped up scrubbies Clive! 

I only asked to see if they were safe as a bulking agent to save on soil - 25kg for around 15 GBP


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## Edvet

I used to put a batch of small lavastones in my sump. Worked great


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## Zeus.

Andrew Butler said:


> You do like your chopped up scrubbies Clive!



Clive was commenting on the use the lava rock as a filter media, the chopped up scrubbies work out cheaper




Chop them up so they fit in filter


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## Andrew Butler

Zeus. said:


> Clive was commenting on the use the lava rock as a filter media


I realise that, I think it is amongst his most published phrases on here - that's why I commented.


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## AverageWhiteBloke

I think there maybe some benefit in fish only systems would be my take on it. We are dealing with things here on the microscopic level, the friendly bacteria just want something to cling to so in a planted aquarium the optimum medium to use would be something with maximum surface area which causes the least drag, poor flow is the no1 issue and the surface area secondary to that. Hopefully most people clean out their filters quite often and a fair amount of bacteria are lost during that process which quickly build back up anyway in an established tank. Realistically it's the plants we want to do the filtering job as they are much better at it than the canister filter and they would rather have the flow.

In a fish only system, I would guess sintered glass, lava rock and all the very porous type medium would have a lot of anaerobic dead spots internally as the oxygenated water only passes over the surface, the inside will fill with anaerobic bacteria which could be quite effective at stripping out nitrate over time but as we are not in the business of stripping out nitrogen, in fact adding extra, you have to look at what would be the best in a filter regarding water passing through it. Obviously its going to be a lot easier for water to make its way through loads of scrubbies with lots of routes through than a load of rocks with limited paths the water can take.

As a bulking up medium lava rock is perfect as its inert, bulky and has some nutrient absorption qualities and wouldn't look out of place if it popped up out the gravel when it settles. My only suggestion there would be that plant roots can't make their way through it as say a mesh bag of cheap gravel. The only downside to the bag of gravel would be you either have to go in a shop to buy a pair of tights or worse ask the OH to get some or explain why you want a pair of her old ones. That's going to take some explaining 

Lava rock is also better in a sump than a canister I would guess as it has the option of passing over it if on the bottom rather than make its way through it.

Just my thoughts on it, they could be all wrong though, I usually am. I'm just thinking I don't think it advantageous to spend $$$$$$$ on the latest nutter bstard canister filter then choke it up with a load of stones drastically reducing the flow through it.


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