Not sure of a replacement? but if I were you I would start asking around to everyone you know that has or has had a dog, chances are someone will have it sitting around in a draw some were that they didn't finish giving it to their dog.
Then after treatment hopefully you have looked into "Bayer" as a dip and dip everything new before it goes into your tank to kill any new red bugs you mite acquire. :wink1:
I actually do have some. I treated my tank last year. I got a prescription from my vet and he recently informed me that it was discontinued...that why I'm asking what replaces it.