I don't believe the intention of 680.51(A) requires you to include your sump pump as a part of "fountain equipment".
The submersible pump they refer to is a pump that would sit at the bottom of the reservoir that is filled with the water that you are circulating through your fountain.
I think you can remove the GFCI from the sump pump.

[This message has been edited by Redsy (edited 03-13-2002).]