If you have determined that the amount of scratching is excessive (based upon whatever criteria you are applying), then my advice is to treat the tank for 3 days with a broad-spectrum antiparasitic med. I can personally recommend Jungle Labs Parasite Clear. Others have used Clout successfully. The Jungle Labs med will have no effect upon your biofiler...not sure about Clout. Give them a SINGLE DOSE and allow it to remain in the tank for three days. After treatment, perform a 50% wc and I believe that you will see a significant dimunition in the frequency of scratching. I'm sure you are aware that Dats like to scratch and you will probably never totally eradicate this behavior.