Aiptasia is a PITA. Hot water will work provided that the water that gets into them is at least 70*C. IMHO, it's not going to work unless the needle is at least 18 guage and you are pushing hard and fast on the plunger.
Heat will denature enzymes and mess it up. But it has to be exposed to higher temps to do any seroius damage to the aiptasia.
What I do is get a syringe with an 18g needle, mix a teaspoon of Kalk powder in a shot glass of water, suck up the powdery solution, turn off filter/powerhead, inject aiptasia. When the aiptasia retreats into it's crevace, cover the crevace with kalk powder. You may have to do this a few times for big ones.
HTH