you would increase your odds for successful treatment, if you could identify a food they will mouth, and premix the metro into it. treating a water volume (with metronidazole) is pretty much an impossible task, IMO. you could try scenting the feed/drug mix, with a few drops of garlic juice, to help convince finicky fish to mouth it. metro treatments should run for 10 days, while dosing in 8-10 hr. intervals. water changes as usual.
if the fish has no interest, in any attempt to feed, then i would switch to a medication that has better success with volume water type treatments. 'clout' is a good choice. HTH.
if the fish has no interest, in any attempt to feed, then i would switch to a medication that has better success with volume water type treatments. 'clout' is a good choice. HTH.
