i don't see any reason why you wouldn't be able to add plants to a tank with an ugf if you are using the right kind of plants.. a lot of plants don't care for gravel, and some don't create a tangled mass of roots...i also think it would take quite a lot of plants to clog up the filter but i agree that it's not good to have them directly in the gravel just for cleaning purposes.... try adding some plants that like to attatch to rocks or driftwood or some floating plants...these are good for beginner plants because they are easy to move around in order to keep up on tank maintenance...i've also seen some people keeping their plants contained in a pot filled with gravel, never tried it but it seems like a good option.....good luck with planting and don't feel too bad about having an ugf..they are not top of the line, but i still have one, it needs a lot of maintenance but it serves it's purpose well