So I picked up some super porous black lava rock for a shrimp tank I’m getting ready to build. It has what looks like mineral buildup all throughout the holes and crevasses. I hosed them off and tried brushing with a nylon brush but it’s not coming off. Any suggestions for cleaning this kind of rock? I assume if I leave it on, it will slowly dissolve and harden my tank water, which I don’t want.

I did a vinegar test and it didn’t react.




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You could soak it in a bucket of water for a week or so to see if it impacts parameters. My guess is that it won't do much of anything.

Just clean it off and scrape away whatever's loose.

I actually just put a chunk in bowl of water, rubbed on one of the white spots and swirled the water a bit after I posted this. When I came back a few min later, my TDS had gone from 5 to 13 in the bowl. I'll try soaking some without disturbing it and see if it still has an impact.

After you let it sit for a while, try testing some other water parameters to see if anything has changed.

Looks like regular old mineral deposits to me. But worth making sure if you have any personal concern.

You could try some CLR and see if that does anything to it.

You could try some HCL from your local hardware store. If you do, handle with care and dilute in water, but it should easily eat away the mineral deposits.


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My concern with using chemicals is not being able I get it all out after cleaning. These rocks leak water for days after being taken out of the bucket and I can imagine not getting some acid out.

Anyway, TDS went way up overnight but I’m gonna test all parameters after another rinse and another round of soaking.


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There's a whole thread on this. HCL will eat up the dKH in your water and lower your pH, but in small doses, isn't harmful. It's regularly used in swimming pools.

Good to know, thanks!

I tested the water again this morning and the ph was up to 7.8 after starting at 7.0. I’m leaning toward cutting my losses and looking for something else to use for my hardscape. Bummer.


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Bummer indeed, that's a beautiful rock.

Before you give up... maybe give it a few days or a week soaking in water. Then do a hard rinsing and brushing. That may be all you need.

It's entirely possible it's just calcium deposits of some sort that's easy to clean up after soaking.

If you have the time to spare, it may be worth it because the rock is so attractive.

If it is calcium, a long soak in pure vinegar should loosen, if not dissolve, the CA deposits.

To those who've used HCL: soaking afterwards in dechlor should neutralize the CL so it's safe to use, no?

Some safe alternatives the HCL are vinegar, citric acid, ilugols iodine. I have used vinegar and citric acid in my my micro fertilizer solution and used the iodine to treat a iodine deficiency without any observable harm to inhabitance of the tank. All will remove calcium magnesium deposits without affective the rest of the rock. HCL is much more aggressive and it can hurt you as well as the tank.

Quick update, after another few days of soaking in fresh RO, ph stabilized around 7.5 and tds was at 62 ppm. Gh is 5-6 and kh is 4-5. I went ahead and put them in white distilled vinegar today to soak for a while. We’ll see how it goes!

Update: I soaked them in vinegar for 3 days and the stuff I could get a brush on came off easily. Still seeing some funk down in deeper holes but the rock is much cleaner looking with most of the deposits gone. I rinsed them a few times and soaked in RO overnight. So far, TDS has not risen in the bucket. I’ll test all parameters after a few days but I think I might be in the clear!

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