You can have one in your discus tank, specially if it is a planted tank, it can help you cleaning the glass. Also keep in mind plecos poop a lot in turn not so good for water quality.The recommended pH-value when keeping Royal pleco is 6.5-7.5. The temperature should be in the 22-30 degrees C (72-86 degrees F) range. The water should ideally be fairly soft, from 2 dH to 15 dH.