wow omg that is terrible idea. if anything clove oil i will use. YIKES!
If you do use clove oil, mix a dose vigorously in warm water first before using it, it does not mix easily with water straight from the bottle, and check to make sure it isn't mixed in alcohol, like it sometimes is.
Don't think I have to explain why breathing alcohol is not a pleasant way to go.
Clove oil takes too long causes too much stress and I do not recommend it.
I think the main trouble is that in many of the guides I have seen to using clove oil there is no mention of how it tends to work very slowly if not pre mixed in some warm water, and this can cause a stressful delay.
The advice of some online guides to mix it in alcohol does not help in the slightest.
Also one of the uses for clove oil in humans is topical numbing for a toothache.
Going by this, I would imagine that it would feel akin to full body novacaine to any fish it was used on.
Based on this, I'm not surprised that one website selling it as a fish sedative mentioned that it could cause the fish to act disoriented before going under.
Here is Nathan Hill's take on methods to use (and ones to avoid) when humanely ending a fish's suffering, in a Practical Fishkeeping article I came across.
https://www.practicalfishkeeping.co.uk/blog/articles/painful-fish-deaths-you-might-be-guilty