Your "needle fish" is most likely a small asian gar,Xenentodon cancila which is not to say it will stay small for long. These fish are skittish and jumpy, and with your Red tails/ Rainbows may not be a good match. You may have a few dead fish from stress. As far as the injury goes, I would watch it and keep close watch on the water, doing your changes is a good thing....If you keep your water pristine it will most likely heal on its own. Keep a tight canopy on as well as many of these fish will jump at shadows and end up on the floor........Hope this helped, D

