I added Wisteria to my tank about 2 weeks ago and it has suddenly taken off, only a couple inches below the surface. I understnad that if it reaches the surface, it will change to the land variety. How do I prune it to keep it short? Do you just cut the top off and replant it? I actually read somewhere that you could lay it flat on the bottom and pin it down to get it to grow horizontally instead of vertically.