Do you put fondant in the Feeder in the Apidea or give them an extra two mini frames (and allow them to fill them up with stores), I can't really see where you could put fondant in an Apidea, although I have seen a beek cram fondant into / just under, the lid of an apidea.
The general consensus here in NI is that you cannot place fondant directly ontop of the top bars as it will drip down between them, so a mesh too small for the bees to get through (like the mesh used in varroa floors in OMF) is place under the fondant, and this is placed ontop of the top bars (plastic wrapping/container is placed over the top and sides to prevent it from drying out).
NB: I have never used fondant, but intend to use it next year with my apideas.