Who Gives A Fish Forums

Been keeping Discus for a year now, but still unsure about water change volume. I do 30% twice a week in my 75-gallon tank with 6 adults, sand substrate, and a Fluval FX4. They're fed beef heart mix twice daily. Should I bump it up to 50%? Water params are good, 0 ammonia, 0 nitrite, nitrate stays around 10 ppm. Just wanna make sure they're thriving, ya know?