Thank you Fishorama, that was a great article.
My nitrates are always low at about .5 with occasional .10. I think the problem is that I used that black eco-gravel as the base level of my substrate then put smoothed river gravel over that, but during gravel vacuuming it has brought up the rougher eco-substrate to mix in with the regular gravel. I think that's what is doing the barbel damage. Two of my corries have no barbels at all now. I'm setting up a 10 gallon with sand substrate and want to transfer those 2 corries to see if they can recover, but then I worry about the other 3. If I transfer all five into the sand substrate tank, what can I get for my 29 gallon? Will Kuli loaches do the bottom feeding like the corries?