I highly recommend euthanizing the fish in a separate container that you can either clean or throw away. Additionally, you won't need as much as you would in the 29 and the fish will be affected much quicker in something smaller.
I have a bottle of clove oil and could give you some if you'd like. I'm home all day today and tomorrow.
As far as the amount, I pulled this off another forum. When I've used it in the past, I have frozen the fish after just to be sure.
1.) Get yourself an empty milk or water gallon jug, cut out the top of it so it's wide enough to put a fish into it easily. Then fill it up with water from the same tank your fish is in & add the fish to the jug.*
2.) Mix 3 drops of clove oil into 1 cup of water. Once you've mixed the clove oil & 1 cup of water thoroughly, add it to the gallon jug with the fish in it. Within a couple of minutes you should see your fish get "sleepy" (e.g. swimming wobbly).*
When you see this you can go ahead and add another 3 drops to the jug. Your fish should then float up to the top like it's dead, but it still might be breathing. Wait another 2 - 3 minutes & add another 3 drops & observe. Your fish should be dead by now, but if not, then go ahead and add a few more drops until it is no longer breathing. The amount of clove oil you'll need will vary from fish to fish.
The key is to introduce the clove oil gradually (not all in one shot) in order to minimize the stress to your fish.*
When your done throw out the gallon jug. Clove oil is potent & being an oil it's hard to rinse off well.
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