Related Clues:

• Izaak Walton's ''very subtil fish''
• Be too picky
• Be a fussbudget
• Minnow relative
• Gripe, gripe, gripe
• Bottom-feeding fish
• Petty objection
• Bottom feeder
• 21-Across. e.g.
• Fault-find
• Koi
• Find fault with unnecessarily
• Find fault with fish?
• Be a nitpicker
• Nitpick incessantly