for them to be really happy they need sand im afraid, they will survive in smooth, small rounded gravel, but as i said they need sand to be happy. They love zooming aand burying in the sand and gravel can ware away there barbels, you could have a nice group of at least 10 i recon, what size is your tank, 240l-260l
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It's up to you KISSfn, if it was me I'd be a little concerned about the barbs being a bit aggressive for the shy cory and I also read somewhere about tetra's pecking at cories eyes (probably a one off though) but if you give the cories hiding places it could work out.