Originally Posted by mrdbdigital
Can anyone here describe the relative particle size difference between regular Black Flourite substrate, and the Black Sand Flourite?
And, are either or both suitable for not damaging catfish barbels?
I've never used either, but just a few days ago I was in a pet store looking at substrates and took a good look at both of the fluorite options. The sand is, as you might guess, a very small size (1-2 mm I'd say). It's a very fine sand, seemingly a little finer than most pool filter sand or reef sand. Pretty close, both in color and in size, to Tahaitian Moon Sand (if you've ever seen that).
The (regular) fluorite is a bit larger, irregularly shaped. Pretty similar in average size to your typical gravels, maybe a tad smaller, but the size varies a lot and the individual particles are not necessarily round but sometimes more of an oblong shape.
As for using it with corys, I am sure either would work fine in terms physical damage to the corys barbels. That being said, I suspect corys would enjoy the sand much better, being as they could really "root around" in the sand when they are exploring, whereas with the regular fluorite they would likely be just on the surface.
In the end, I like them both. On one hand, the sand is really quite stunning looking in a tank. On the other, the regular fluorite is probably a bit more "natural" looking, since there are variations in both particle size and particle shape--something that is going to be a more accurate replica of natural freshwater environments in most cases.