If you don't mind artificial plants here is an easy and cheap way to make them into floating plants. All you will need is a cork, nail or something that'll poke a hole in the cork and of course the plant. Take your plant out of its base, the newest ones I had to break out with a hammer. Clean your cork and take an appropriate sized object, something just a bit less in diameter than your plant stem, to put a hole into the cork. Next take the stem of the plant and shove it into the hole in the cork. It should fit snugly. Toss it in your aquarium and you're set!