I have three fish, two of them have picked up the habit of sucking air after every meal to the point that they float helplessly for hours. It's been a nuisance, but it got serious this morning when I noticed a reddened patch on my celestial's back, presumably from his slime coat drying out. I'm afraid of it becoming infected.

I'm 95% sure it's not an aeration problem, I have two power filters and a bubble wall. My fantail has absolutely no inclination towards doing this and they only do it after eating. Pellets, flakes, peas, worms, it makes no difference.

I've tried startling them whenever they go to the top, but they ignore me eventually.

What can I do?

Emsley my oranda does that, I dont know why he does it, maybe he's hoping i'll give him more food or something He is getting kinda floaty sometimes.
I know that you can put a bit of vaseline on the bits that stick out the water, to stop it drying out.. I dont know about putting it on now though as theres already a red bit.
But I've no idea how to stop them doing it.

My two baby ryukins do the same thing, but they haven't started floating yet. I don't know why they do it.