I have had my new tank cycling for 2 months before putting fish in it. I tested it with the API test kit and all levels are within range.
I brought home 6 celestial pearl danios and 12 red flame tetras today. The Danios (gorgeous fish!) are fine and 10 of the red flames are too, however, one is behaving oddly. If he stops swimming he sinks like a stone.
Has this fish been injured in transport or is it ill?
Thanks in advance.