Coal Slag as substrate?

[cacas]

I've been considering substrate options recently and I really like the look of black sand. I know that black sand has been discussed here many times, but most of the time it is referring to CaribSea Black Sand / similar products. In the freshwater community, "Diamond black blasting sand" has apparently been used as a substrate; it is made of coal slag. I know that coal slag is mostly silicates and oxides left after coal combustion, and is fairly inert. I'm not too concerned about the supposedly sharp edges as I am fairly confident that reef creatures would be in contact with more abrasive materials in the wild. However, there isn't much reef-keeping history with coal slag online. I am aware that coal slag is an industrial byproduct, so I am worried about possible trace amounts of metal/heavy-metal contamination that could potentially harm delicate reef life.

I did find a thread here on reef2reef but it did not have much discussion on whether/not it would be feasible for a reef environment: Link

My question is, would there be any issue with unknown trace chemistry when using coal slag blasting media as a substrate in a reef environment?

 

[edsbeaker]

I have used it for a freshwater planted tank because it’s so inexpensive, but I remember hearing that it could contain heavy metal pieces in it. I don’t know if it would be worth the risk.

 

[Fish Fan]

Same, I’ve used it in freshwater where is fine, but I don’t think I’d use this is saltwater.

 

[Randy Holmes-Farley Verified Community Expert]

It sounds like a risky idea in terms of metals. I would not recommend it.

 

[cacas]

The tank that it would (supposedly) be used in would be a mainly macro+softie tank. It wouldn't have too much rare/fragile livestock. I might just YOLO it and try it out with some softies and stuff; any input on this idea? Is it too risky or maybe a possible experiment?

 

[BeanAnimal]

It is full of metals. I can’t imagine it even being a remotely good idea.

 

[Fish Fan]

I like a black substrate too, and I have several bags of the Caribbsea Hawaiian Black in my garage that I bought years ago. I'm not going to use them after I've learned of some of the concerns, but if you were closer to me I'd give them to you

I wouldn't use that Black Diamond blasting sand in a saltwater aquarium, and I personally won't use the Hawaiian Black myself, but the truth is a lot of people do use it, and many report that there's no issues. If you're just looking for macros and easy growing softies, I might try the Caribbsea sand. Just keep in mind that if things are not going well and there's no other obvious answer, it may be the sand

One warning; it will for sure have magnetic (metal!) particles in it (which is why I wouldn't use it), and you have to be very careful not to get those particles in between your glass and your magnetic scrapper, or you can severely scratch your glass in a hurry. Razor-type scrapers may be best with this sand.

This is a thread where I asked about black sand, many advised against it, but others said it worked well for them. You can decide for yourself:

Is there a Coral/Motile Invert Safe Black Sand? CaribbSea Hawaiian, Yes Or No?

Hey all! I'm posting this question here in the Chem section to get hopefully some real science and more than just anecdotal observation. RHF, please feel free to move this to the Aquascaping section or wherever it's more appropriate if needed :-) I have always liked the look of black sand, and...

www.reef2reef.com

Good luck!

 

[Mebbid]

In a freshwater tank, the black diamond blasting sand is great. I'd never use it in a reef tank however, there's magnetic particles in it and no guarantees against contamination.

If you want some black sand take a look at the carib sea hawaiian black substrate, I had some before and it's nice