So not really an issue (I hope), but sometimes my BN are darker in color - like very dark, I can't differentiate between them and the dark rocks in my tank - on the other hand, sometimes they're very light. I heard that it's normal and it has to do something with whether they're hiding in caves a lot or not but... is it? Does it mean anything at all? Mood? Health? Either color preferable? Pretty sure my BN are the common btw, but I don't really know how to tell different BN species apart.