Its fine to add water as long as its treated (conditioned) water-it wont affect cycling any respect. I am not sure what is floating on your water. Is it growing on the surfaces in your tank or only floating on the surface? You could try scooping it up or using paper towels & cleaning it off the surface of the water. Also, do a search on here for 'angelsplus' live filters (you should find a bunch of links to their site)- they sell live, seeded filters that quite a few people have used to quickly cycle their tanks.