# Seachem Onyx Sand vs. Flourite Black Sand



## end3r.P (Aug 31, 2015)

I'm deciding between these two substrates for a Fluval Spec V. The tank will house a betta, and I'll be using driftwood and planting just low-light plants -- Crypts, Bucephalandra, maybe a moss or two. I will use Osmocote+ Root Tabs.

Seachem says the Flourite Black Sand is inert, while the Onyx Sand has minor KH buffering effect (purportedly raising pH by 0.1 to 0.5 depending on source water). I will be using re-mineralized RO water as the source, which has 0 GH and 0-1 KH.

Any experience with these or thoughts on which to go with? I like the lighter gray color of the Onyx Sand, but I'm wondering whether its slight KH buffering would be a pro or con for my purposes, i.e., starting with RO water and given the plants I want to keep and (and for a betta). I doubt the KH effect will be that significant, and I'll probably be adding a little bicarbonate to new water anyways... but maybe with crypts and buce it's better not to add the additional source of bicarbonates?

(I would use Black Diamond sand for a bigger tank where cost would be more of an issue, but I don't want or need a 50lb bag for this one.)

Maybe one thing that would help: I'm starting with C. parva, wendtii, and willisii (lutea). Are these particular species likely to be helped or hurt by the slight increase in KH from Onyx Sand?


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## Harry Muscle (Mar 13, 2007)

end3r.P said:


> Maybe one thing that would help: I'm starting with C. parva, wendtii, and willisii (lutea). Are these particular species likely to be helped or hurt by the slight increase in KH from Onyx Sand?


I'm assuming this is going to be a low tech tank? If so, these tanks usually benefit from added carbonates since many plants can get their carbon from it instead of CO2.

Tom's famous non CO2 method recommends onyx sand as a substrate for this exact reason.

Thanks,
Harry


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## randym (Sep 20, 2015)

If you like the color of Onyx, go with it. I ran a high tech tank with Onyx substrate for years. The C. wendtii grew like crazy. Fish and plants seemed to love it. 

The only thing I didn't like was...the color. I prefer a darker black. ;-) (There was no Flourite Black Sand back when I set the tank up.)


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## end3r.P (Aug 31, 2015)

Harry Muscle said:


> I'm assuming this is going to be a low tech tank? If so, these tanks usually benefit from added carbonates since many plants can get their carbon from it instead of CO2.
> 
> Tom's famous non CO2 method recommends onyx sand as a substrate for this exact reason.
> 
> ...


Yep, low tech for sure. Sounds good.

Bump:


randym said:


> If you like the color of Onyx, go with it. I ran a high tech tank with Onyx substrate for years. The C. wendtii grew like crazy. Fish and plants seemed to love it.
> 
> The only thing I didn't like was...the color. I prefer a darker black. ;-) (There was no Flourite Black Sand back when I set the tank up.)


Cool. I'm sold. I like the gray look for some reason. I like black too, but feeling like going with something a little different.


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