You need a delivery system.
I used a stick, airline tubing, ziptied the tubing to the stick. At the other end of the tubing, use a syringe from one of your test kits. I use a 5ml one.
The end fits nicely into the airline tubing. That too is ziptied to the stick.
Now I can "suck" 2-3ml of vinegar - what I smother my aptesia with - and move the end to be right over the "hole" the aptesia hides in when I get close. Squirt.
At the end of my stick, I made a 90 degree turn with a ziptie, so I can squirt sideways. The stick is an aquascaping stick, a wooden dowel would work.
At least this way, I can sneak up on the little guys, and the vinegar makes their tentacles turn white. I think they can't catch food anymore and die.
I also have a filefish, but he doesn't chow down on the big ones, so all the big ones got vinegar. I don't have any peppermint shrimp. A boxer & and cleaner shrimp.
It's been months since I've seen any evil dudes lurking.