Pl*cs and sand don't mix, they stir it up plus it's not meant to be good for them.
Black sand is tahitan moon sand (or however it's spelt), not cheap.
If you want sand then anything inert (not marine) - silica sand or play sand is fine - silica sand looks stunning (pure white) but sand does get dirty quickly.
I sort of regret having sand in my 14g, it looks good for a day or so after cleaning it, then looks messy after that.
Both my catfish tanks are sand substrate. Once you get the hang of the best cleaning method for it it's fine. Anything bigger may risk damaging their 'whiskers'. Especially the more active species. I have silver sand in mine and it works very well. When they disturb it it falls back down rather then floating. The only problem I seem to get is that when they have a real barmy moment any plant not very well anchored can be uprooted and you end up having to put it back in. It's rare that a day goes by when I don't have to replant one or two in the 55g.
Hugs,
P.
I have playsand and within a day or two of vacuuming it it's back to dirty again (particularly when you have an overstocked Mbuna tank ) .
I am actually that fed up of the sand, my weekend chore is to empty the tank of its contents and inhabitants and replace the sand with a really fine marine gravel (to keep the pH buffered).There is a little of it in the tank at the moment and the fish seem far more "impressed" with this than they are sand. Always busy digging their breeding pits.
I have never heard of any problems keeping Plecs in sand (other than the digging). If anyhting it will be more natural for them. All mine love it, and if you have live plants then they can trap a lot of the crap. I have sand in every one of my tanks ranging from 4 to 180 gallons and never have to siphon off for stuff lieing on the surface.