# Are rainbow pebbles safe?



## Emil. (23 Feb 2020)

Hello All,

Does anyone have any experience with "rainbow" pebbles from b&q garden centre section? My girlfriend really likes them so I'm going to incorporate them in an aquascape.

I'm assuming they'll be fairly innert since they are pebbles, right? Please let me know if you think it might leach something nasty. 

Thank you!


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## Kezzab (23 Feb 2020)

I suspect they are fine. Are they quartz like?


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## Emil. (23 Feb 2020)

They are not quartz like. They are, however, surprisingly light. Feels like holding a piece of concrete. I bet they can be broken down easily with a hammer.

I took two out and washed them. They have less colours than real rainbow. Whew!


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## tam (23 Feb 2020)

It says 'Suitable for use on water features' in the product description so I would imagine they'd be fine.


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## Andrew Butler (23 Feb 2020)

Emil. said:


> I'm assuming they'll be fairly innert since they are pebbles, right?


My input; rightly or wrongly.........

Give one a clean just to remove any dust etc and let it dry out, then try putting some vinegar on it; if it fizzes/bubbles/foams then it will effect the water hardness in some way.
Some pebbles and stones are not formed naturally but by simply tumbling the smaller pieces of stone from quarries which these could quite possibly be and I suspect they are a sandstone of some description, especially if you say they are very light.

It may be worth remembering that not all water features include fish


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## Kezzab (23 Feb 2020)

Either way, all they are possibly likely to do is up your water hardness a bit.

There shouldn't be anything toxic.


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## Emil. (23 Feb 2020)

I put viakal on and it doesn't fizz. Yay! I'm mostly worried about it leaching silica. Is there any way to test for that? Or would silica cause fizzing too?


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## jaypeecee (23 Feb 2020)

The one shown in your hand looks very porous. Are you sure it actually sinks?

JPC


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## Emil. (23 Feb 2020)

jaypeecee said:


> Are you sure it actually sinks?



Haha, it sinks.


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## dw1305 (23 Feb 2020)

Hi all,





Emil. said:


> They are not quartz like. They are, however, surprisingly light. Feels like holding a piece of concrete. I bet they can be broken down easily with a hammer.





Emil. said:


> I put viakal on and it doesn't fizz. Yay! I'm mostly worried about it leaching silica.


I’m surprised They look like they are “travertine”, which is calcium carbonate.

The other most likely option is that they are volcanic. I’m not sure the silica bit is relevant, but they would be silicate based if they were volcanic.

Cheers Darrel


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## jaypeecee (23 Feb 2020)

Emil. said:


> Haha, it sinks.



Excellent!


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## Emil. (24 Feb 2020)

dw1305 said:


> The other most likely option is that they are volcanic. I’m not sure the silica bit is relevant, but they would be silicate based if they were volcanic.
> 
> Cheers Darrel



Hi Darrel, I read somewhere that leaching silica feeds brown diatoms. If it's true, I'd like to a avoid that. But I don't really understand any science behind that claim. Or where it came from. My geology knowledge is pretty much nonexistent. 

Having said that, I think you're right about them being volcanic. Poking cracked one with the tip of my finger felt like poking a lava rock. It breaks into tiny sand like particles.

I'm gonna go ahead and used them in a tank. I'm also going to procure TDS meter to see if I can measure any changes.

Thanks everyone!


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## Gill (24 Feb 2020)

Have been using Rainbow rocks for a while now. And you can find the larger peices carved into nice structures in decent LFS. Got it from B+Q for the Garden, but liked it so much more in the tank.
Algae grows on this rock very quickly and is great for attaching moss to and epiphytes etc.

I have not noticed any degradation of the rock while in the tanks yet, but saying that I rotate them with the outside ones that have algae growth on them for the shrimp and algae eaters.


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## Emil. (24 Feb 2020)

Excellent news! Thank you, @Gill


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## dw1305 (24 Feb 2020)

Hi all,





dw1305 said:


> The other most likely option is that they are volcanic.


Better monitor, and they look even more like travertine, although sandstone would also be an option.





Emil. said:


> If it's true, I'd like to a avoid that. But I don't really understand any science behind that claim. Or where it came from. My geology knowledge is pretty much nonexistent.


Diatoms are really interesting organisms, they are pretty much universal anywhere there is water and they are extremely efficient at extracting the silica that they need to build their skeleton (frustule).

Have a look at <"Too high silicates..."> and <"Diatoms - My....">.

cheers Darrel


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