If you did not use Tetra AquaSafe® to remove the chlorine, the fish gills are being burned. This will cause the fish to dart around the tank. If it has been fewer than 24 hours since you added the fish, add Tetra AquaSafe® now. After 24 hours, the chlorine will evaporate out of the system, but the damage will already be done. This behavior can also be caused by fish fighting. Make sure another fish is not harassing the distressed fish. If this is not the case, test the water levels for ammonia, nitrite, nitrate, high pH, and incorrect temperature.
