Thanks. I let him go as it looks like a sponge eater and in 380 gallons there is a lot of sponge for him to eat. Seen him once more since I let him go. Seems harmless.
Some nudis are indeed toxic, but a lot have very specific diets that we cannot provide them with long term. As they slowly starve to death, their ability to 'nuke" a tank diminishes, so they basically aren't a threat, except in the smallest of tanks. In a 380 gallon, the point is moot and he's super cool.