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Help with rock identification

1780 Views 11 Replies 8 Participants Last post by  Max

I have recently purchased 2 stones from a LFS at a considerable discount. The stones were sold as 'Volcanic' rock. I googled for it in terms of aquascaping and found no information specifically on these stones. I did found instead a lot of info on lava rock which does not look like the stones that I have. The lava rock is pumice most of the time and will float. These stones are heavy relative to the pumice. I was wondering if anyone knows this type of stone? Are these safe for freshwater planted tank? Thanks in advance for any info.


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Not sure just guessing, it looks like petrified wood to me, again just guessing.
Not sure just guessing, it looks like petrified wood to me, again just guessing.
From my limited knowledge of geology and types of rocks, the stones probably have some iron in them due to its excessive reddish colour. Not certain but it might have as well some feldspar (I need to check this).
Looks like ohko stone to me. If so yes its safe.
Looks like ohko stone to me. If so yes its safe.
Yes it does look like ohko stone. Thanks for hinting!
As little as they know at the rock yards, that could really be volcanic rock. You may find more aquarium uses under 'lava'.
Generally this sort of rock is safe. Whatever minerals are in it got well locked up in the heat.

As always, though, you can sure test it: Put it in a bucket with some water prepped however you will do it for the aquarium. Test GH, KH, pH, TDS when you start, then the next day, then every few days for a week.
Minor or no changes is fine for that set up.
Major changes would not be good to use the rock in that set up.
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To me, that does look like petrified wood. If that's what it is, it's aquarium safe.
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I have looked again and again at the stones and compared with similar stones and I think now that it is not ohko stone. I do agree that it might look like petrified wood though I am still not certain about it.
If unsure, do the acid test (literally). Those rocks look really cool though, I suspect you got a steal of a deal.
I have local rocks from the NJ Highlands in my African Cichlid tanks that have streaks of iron in them. I just tested one of my tanks for iron using a Hach test kit and I got a zero reading.

Last water change was maybe 3 weeks ago. Tank set up for at least three years. Hard water, pH 8 or so. No plants.

I don't worry about iron anymore.

My first impression of your rocks was Petrified Wood also. It looks like it has been cut and polished in areas.
Definitely ohko stone.
Its a mud-rock with channels from rising gas which is solidified, I believe it would count as volcanic.
If you put a drop of nitrate test bottle 1 on a rock (its hydrochloric acid I believe) and it doesnt fizz then it is likely inert - or at least the acidity in the water wont dissolve it.
If it does fizz then you could still use it but it may affect your water.
Thank you everyone for suggestions.
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