• Some slabfishes unobtainable by breeding are present, like skeleton, brown mushrooms, and ghost slabfishes.
• The advancement triggers when you breed a specific slabfish instead of when a specific type of slabfish spawns from being breed. To clarify, when you breed two warm ocean slabfishes, the warm ocean slabfish will trigger no matter what the resulting slabfish is, but if you breed slabfishes (other than warm ocean slabfishes ofc) in a warm ocean biome and resulting in a warm ocean slabfish, the warm ocean part of the advancement will not trigger.
• Icy slabfishes are listed in the advancement code and don't seem to exist
• Snowy slabfishes are not listed at all, probably mislisted as the icy one lol. This means that the advancement is currently impossible

oops i'm stupid basalt deltas does have an s