OK I'm up to 2 cups a week of rid-x in a 300 gallon tank 85 fish tropheus plus 10 assorted cool plecos . I still need more, my Demetrius is down 60-70 % but my filters 3 filters one sump 2 pumps 700 gpn plus 2 eheim filters 2262 in 5 gallon containers get real real dirty have to clean every 2 months . I did think the filters would be cleaner due to rid-x but nothing is perfect I'm happy as a clam with results