While in the haste of getting ready to go to a Christmas party I asked my hubbie to do a partial change-out of the water in the tank (55 gallon) because I had accidently over fed our Raphael his favorite shrimp pellets yesterday and the water was cloudy. I am not sure he de-chlorinated it, and we were gone five hours before I came home to all of the fish out of their usual hiding places, some at the top breathing heavy and fast. We have lost an Angel and a Rainbow fish so far. Tank not overstocked, ammonia 1ppm, nitrate 6.0. I immediately put in de-chlorinater just in case, and a little slime coat additive just for good measure. Was I too late? Can the others possibly be saved? We have a fresh water lion fish that will break our hearts if he passes.......................