Not saying it isnt a parasite, but couldn’t it be due to water quality as a more plausible explanation? OP said his gar had a decolourised nose, so I would lean more towards internal issues/ water quality.Cyprinids like pond raised feeder goldfish, and wild caught minnows and tetras, are notorious carriers of parasite such as Lernaea.
Even frogs and tadpoles can be carriers
Using any of the above as feeders (without a lengthy QT period) and thorough examination of each individual before putting it in a tank s a feeder, s a very risky proposition.
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All it takes ia one carrier like the tetra above with 2 parasites on the lower jaw, and a couple on the dorsal, and the population of an entire tank can be wiped out in a week.
This is why I would never use feeder fish with my predatory fish.
I will starve a fish for a month or 2 in an attempt to convert it to pellets, before I'd subject a tank to using feeders.
hard to tell from the picture OP posted for sure however