Look at Dennis pictures and then rethink this. I would want a dslr to capture the full beauty of your 300g tank.
This should be high on your tank list. Take a look at Dennis pictures and then try and redo them using a point and shoot camera. And with a tank like your planning I would only want a camera that going to be the best. What about a rebel T3i or Nikon D5100. Each are $850 with a bundle package.