Painting tank screw up

[Seamonkey]

Hi, Need help!

A while ago I asked if anyone had experience with painting the exterior back of the tank instead of taping on one of the plastic sheets you buy from petstore.(I always get wet area's and salt creep).
I recieved some input and decided to go with the exterior latex, against the paintstore warning that in no way it would work, as the paint has no way to stick to glass. I went ahead and painted on one coat, looked a little scratchy, but the second coat actually started to peel it away, now it looks like **$#**! Basically did not work, as the paint store stated.
They said a light sanding was what would be needed, prior to the paint application. (I'm a little leary of doing this incase it looks worse) At this point I have to clean it all off and either try again or give in to taping.
Has anyone ACTUALLY ever tried this and had success. Let me know, as I am willing to try it again.
Thanks