I have 4 otocinclus catfish, and I just recently noticed that there are some little coppery colored patches on their tails. There is just a little break in the black stripe that runs down the tail where it is like shiny copper scales instead of black. 3 of them have this, but some have more patches along the stripe than others. Could this be velvet? i don't think it is but the lfs girl suggested my tank might have velvet, because some guppies i had were flicking in the sand a lot. plz let me know what might be wrong and how to fix it. any thoughts appreciated