trim

My 55g tank that I plan in using for my turtle is on a solid oak dresser and it's pretty flat. But the tank only contacts the dresser on the corners for about 4in then the rest is raised a little (I can fit a quarter under it) I think this may be because I bought the tank when it was like...

Can I cut the tips off my Vallisneria or will it cause the whole leaf to die? The ends of mine have gotten a bit ragged and they dont look very nice anymore. I tried looking it up but I've gotten conflicting information on it. Any one with personal experience?