Spironucleus in Fishes
A close relative of Hexamita, this tiny protozoan can kill fish by stressing them out, and can be hard to diagnose as it is VERY small. Frankly, I have a hard time telling it from Hexamita and who cares, they’re treated the same. Signs of disease are panting fish, weight loss, casts in the poop and pin holes in the fins.
https://drjohnson.com/wp-content/uploads/2019/09/spironucleus.pdf
Spironucleus in Fishes