Chris B wrote:

I have a sick pleco. Not immediately dying but obviously ill, losing
weight, pale, etc. What is the most humane way for me to play Dr. Fish
Death and help this little guy into the next life? Would like to do this,
this evening.

Clove oil.

For small fish:

8 drops of clove oil
24 drops vodka
1 quart water

For large fish:

3ml clove oil
8ml vodka
1 gallon water

I've used this 3 times now. The fish swims normally and slows to a stop.
Leave it in the solution for an hour. While not necessary, I decapitate it
after that just to be safe.

I get clove oil (used for toothaches) at the pharmacy.

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It's turtles, all the way down