yup yup. i have experienced that too. i also bough a diamond goby and the first night i introduced it to the tank, it jumped. good thing I had a tight lid. But then he kept on jumping for about 2 weeks, and it enxded up landing in the filter, where I had to fish him out and that rteally messed up my biological filteration. I lost 5 mushrooms, a large rock of star polyps and a frogspawn coral. now I have a mesh on top of the filter to keep that from happeneing again!