that web site isn't exactly ... correct on a lot of things (for one thing they say that dragon gobies "graduate" to eating small guppies, which i've never seen or heard of). they also have a photo captioned "dragon goby" which clearly isn't correct. i would do more research on the halfbeaks, looking at other web sites than this one. especially look for possible compatibility issues with the knight and the smaller fish. just my humble .02 
