How do I know if my lava rock that I added is aquarium safe?

[Urchin boy]

This is my recently set up saltwater tank that tries to emulate a rocky sea floor environment using pebble rocks and also plenty of lava rock and a few pieces of live rock as well.

I am aware some types of lava rock are not safe to use because of heavy metals and that kind of stuff and for other possible reasons like silicates .

As I am not going to add anything in this tank for a long time to let it cycle first and establish a bacterial colony I would also like to test my parameters to see if this can be used or if I need to replace it with live rock instead.

What do you think?

I got my lava rock and pebbles from my local aquarium shop and was told the lava rock would be inert and should not affect my pH .

 

[tzabor10]

Your setup looks great.
If your LFS sold it , it’s probably ok.
What do you want to do with the tank?
If you want fish, I’m sure they would appreciate a place to hide.
Good luck

 

[Urchin boy]

Your setup looks great.
If your LFS sold it , it’s probably ok.
What do you want to do with the tank?
If you want fish, I’m sure they would appreciate a place to hide.
Good luck

I am aiming to replicate a Carribbean ocean biotope with no corals at all with a focus on sand dwelling fish and invertebrates like sand dollars and yellowhead Jawfish that need a deep sandbed to be happy.

I do know yellowhead Jawfish like to dig burrows in the substrate to hide in there and this is even something they especially do when they have babies and eggs which are carried by the father in his mouth so I would like to obtain a healthy pair of them so that maybe I can see this myself.

I need to seed my sandbed with critters like bristle worms snails and others like it that help stir the sandbed after I have increased my sandbed to at least 10 centimetres or more making sure everything is cycled before adding them which could take months before then.

I tried to make some caves using my lava rock and I thought it looked really nice and I do have some aquarium safe glue that I can use for aquascaping.

Posted it about it on Reddit but was promptly told to not use them because they can leach stuff like heavy metals and silicates and honestly I wonder if they have even tried it or if they are just parroting what they read online.

 

[ISpeakForTheSeas]

Posted it about it on Reddit but was promptly told to not use them because they can leach stuff like heavy metals and silicates and honestly I wonder if they have even tried it or if they are just parroting what they read online.

Most likely parroting - the leaching is theoretically possible (and may tie in to the increased algae growth discussed below), but, as mentioned below, I've yet to see an example of a tank being unable to sustain corals, inverts, or fish due to the use of lava rock (and I have seen several tanks use lava rock or other "freshwater" rocks successfully for all of the above):

This has been a controversial topic the few times I've seen it come up - long story short, I've never seen a tank crash (i.e. with things dying in it) from the use of lava rock; I have, however, seen lava rock taken from a freshwater setting and reused in a saltwater setting that had major algae problems for about a year (presumably from built up nutrients and/or iron in the rock).

That said, in theory (I've never seen this actually proven to happen in practice), lava rock can leach toxic metals into the water, so to responsibly use it, most people cure it for a decent length of time (several weeks; preferably with RO/DI water because you know it's not adding anything unwanted to the mix).

I don't have much in the way of ideas or advice, but with regards to the volcanic rock (scoria rock being the kind of volcanic rock typically used in aquariums): long story short, yes, you can use it (but it's probably not ideal).

People will likely warn you that it could leach toxic metals into your tank and nuke it. This is technically theoretically possible (and there is some slight evidence at this point to suggest that some leaching may happen and cause increased/prolonged algae issues/ugly stage issues - though the instances I have seen in depth info for with this had many other variables at play as well), but I have literally never come across any evidence of this leaching causing tank crashing (or even inverts dying from leaching copper) despite actively looking for it. So, as long as you do watch for issues, you should be fine.

*(In complete seriousness, if anyone has solid evidence of tank nuking happening as a result of the use of lava rock - even anecdotal evidence that just ruled out all or most other potential causes of issues - I would genuinely love to see it; all the evidence that I've seen so far - which involves very few claims of the rock actually crashing the tank - had about a thousand different variables involved that could have caused the crash regardless of the rock.)*

That said, here are a couple of other points that are definitely valid: volcanic rock tends to be sharper/more jagged, and can more easily injure fish (particularly depending on the fish kept in the tank); and volcanic rock lacks the pH buffering abilities of calcium carbonate rock.

And here's a breakdown of the average composition of lava rock just because (scoria is vesicular basalt, so the basalt category would apply to it):

What is lava made of?

Lava is made up of crystals, volcanic glass, and bubbles (volcanic gases). As magma gets closer to the surface and cools, it begins to crystallize minerals like olivine and form bubbles of volcanic gases. When lava erupts it is made up of a slush of crystals, liquid, and bubbles. The liquid...

volcano.oregonstate.edu