I have a male betta with 7 neon tetras in a 20 gallon heavily planted aquarium. Since last month, my betta has cloudy eye. I used Melafix and the cloudiness got removed in a day. But again within a few days the betta had cloudy eyes. This time I treated him with melafix for 7 days as instructed on the bottle. The cloudiness was again fixed within a day I started the treatment. Today, I saw that it again has cloudy eyes. Now I feel bad to treat him with medicines every few days and want to know what’s causing the cloudiness in his eyes. My water parameters are fine (ammonia, nitrite 0ppm and nitrate between 10-20ppm, ph is 6.8 but when I turn on the co2 it drops to around 6). The only probable cause I can see is the pH of the water. My betta eats normally and there is no change in his activity level. Can anyone tell me what could be the cause of cloudy eye.