This could possibly be a symptom of Swim Bladder Infection which is usually caused by over feeding. Ideally you should only be feeding 4 pellets daily. My recommendation towards treating this would be along the lins of introducing a dose Of Epsom salt at around 1 teaspoon per gallon
- eradicated swimming
- floating towards the surface of the water
- trouble swimming up
- seems to be doing "rolls"
Treating this usually non fatal illness will be very easy to do. Usually a dose of aquarium salt, something along the lines of 1 teaspoon per 3 gallons for tetras, and 1 teaspoon per gallon for more salt tolerant fish such as Bettas. Typically after 1-2 Epsom salt treatments it will go away. Ideally during this treatment time you would also want to offer peas, and daphnia to the fish as this will also help
This illness is usually caused by incorrect feeding with diets that have little or no nutritional value, or over feeding. Or incorrectly feeding more than the needed periods in the day to feed, like feeding very often
This illness is easily prevented by going along the lines of not over feeding, providing a varied diet with many good foods, and feeding lots of low nutritional value foods