[Deborah]

I would pot up, but before that hose away as many ants as you can.
I'd buy cactus mix for soil.
Meyers I water like anything else-stick a finger down and feel for dryness, and flood until the water runs out.
Feed with citrus food. Lemons are heavy feeders.
When you repot you'll smother the ants. And drown them when you water in the newly planted tree.
Ants can't harm the tree at all but I'd get rid of as many as I could. If you don't have pets nearby you could put out ant baits near the pot.
If anyone has any other ideas I'd welcome them-I love my tree and always glad to learn. Won't get offended if corrected either !