I have noticed, having kept a couple Niles, that they do flash occasionally .... it could be a sign of parasites, and if he starts doing it more often, then I'd say def parasites ... the fact that he's eating live also indicates a higher likelihood of parasites ... but if he's doing it very infrequently I'd just be sure to be doing a lot of water changes and adding salt for a couple weeks and watch him, if it gets worse I'd medicate if he stays the same or gets better, then you know your water quality wasnt quite what it should have been for him
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