Betta Fish Swimming Sideways After Water Change. Most fish are not meant to swim sideways or float at the top and bottom of the tank. Betta fish at the bottom of his tank after water change if you notice this happening then there are one or two reasons it’s occurring.
It can potentially also kill them from stress. Betta fish are not strong swimmers and will become tired if the water flow is too strong in the tank. Reducing the water level to make it easier for the fish to move around within the tank.