I'm currently using fairly common light-coloured sand and gravel in my Cory tank. I would like, however, to change to substrate with a darker hue.
I can get hold of black glass-gravel, but it is very spikey and wouldn't be good for barbels at all, although it's about the right grain size. Has anyone come across darker smooth sands and ~3mm gravel? If so I don't suppose you could tell me which brand and where you got it (preferably UK in that case..)? I've seen one or two reasonable offerings on-line, but I'd prefer recommendations from who've coped with the delicate barbles of prime Corys

Cheers,
Greg