Hi,
Not to sure on the american types of pumps, I use a Internal filter but poke it down below the surface with a airline so i just gives out a slow current through the top of the water, i know its pro not the best but i will be upgrading my pumps at somepoint soon.
If this is a bacterial infection a salt bath will do nothing to get rid of this,if it has a fungus it would be ok to salt bath.
If you think it has ate gravel also putting it in the fridge is supposed to make axies poop more often so it may pass it through then and remove it right away or may swallow them again.
As for the tank i would just leave it the way it is,and just check the nitrates Ph before returning the axie to the tank.
Vet cost no idea to be honest ive not had to take any of my axolotls to the vet yet,fingers crossed!!!
Anywhoo i will touch base with you later,follow the fridging and im sure another member will advise if this is bacterial.
Off to bed its 4am in Scotland. lol
