I only fish artificials and never use live bait nor soft plastics, meaning I have never gut hooked anything. Anyway, I'm not saying a fish can't live with internal parasites. If it isn't severe, it might possibly live its life without me even knowing. Despite this, I highly doubt they're going to be able to fight them off naturally. Of course, the most accurate way of identification is microscope, but if that isn't an option, there are obvious signs by just looking at your ray. If it's eating regularly but not putting on weight or is losing weight, or if it doesnt eat at all and is losing weight abnormally fast, it's obvious signs of internal parasites. If one were to follow proper procedure and quarantine everything first, majority of these ID issues would never happen. One would never have an issue of having to dig out the source of internal parasites if the issue is brought up during the quarantine period. If you don't have the space to quarantine, then should you be buying the ray in the first place? Just some food for thought.