Specular Fish

This is the potion fish. Recall and Wormhole potions both run on it, and those two are what you burn through fastest in an active world, especially in multiplayer where the wormhole is how anybody gets anywhere. A deep stack sitting in storage is worth far more to you than any meal you could cook out of it.

It lives in underground and cavern water and it is thickest in the cold. If you have a snow cave with a reachable pool, fish there and nowhere else, since the same rod and bait will pull it up noticeably more often. One sitting at a good snow pool covers a long stretch of potion crafting.