Reply #49: Keep doing it.

[NYC]

If they are coming up the drain, you need to keep washing them back.

Someone once got mites on 3 or 4 indoor geraniums. She didn't notice it until they had spread everywhere. They were even crawling out her doorbell on the front door. (Hers were going out, not coming in.)

If these are coming inside, they must have overrun the plants they were living on. Assume it is a major assault, and keep up the battle. Bugs do come up drains, so I assume that's why they are in the bathtub.

I wonder if adding salt to the water will help. For sluggish drains, you should pour salt and boiling water. Maybe you should take this opportunity to clear your drain while you are battling the invasion. (Also clear out the dead mites in the drain after you drown them.)

Good luck.