Well maybe u could put some stuff around the bottom of the cage or rack whatever your sitting on. like say for example u got a table. And on that table is ur tub.
Well for the ants to get up it they would have to climb up. If i recall theres like a powder you can lay on the floor or some sort of spray. Maybe u could spray it around the base of ur rack if it isnt close enough to harm any of the snakes.
Edit:
Googles sugar ants got this
http://www.getridofthings.com/get-rid-of-ants.htm
http://www.getridofthings.com/get-rid-of-sugar-ants.htm
Maybe could try the borax thing around ur table/rack/stand w/e it may be?