List of Usefull Fish

[Phydeaux]

Pretty much all fish desynths provide Water crystals, and many provide a secondary crystal as well. Most Western Coerthan fish provide Ice crystals for their secondary. While I haven't done much Hellfishing yet, I'm guessing most of those fish will provide Fire crystals as their secondary (or maybe even primary?).

These are not equivalent to Aetherial Reduction, though.

Answering XLauncher, the only one I found so far was the Manasail, Churning Mists, 10am-2pm, yields Water.