I dont have any but I just want to make sure I never get any! I always use RODI water, never run lights over 8 hrs and feed very little, just thought it might be good to have something just in case?
look into a new carbon filter. thats where most of us that run rodi units get our phos from. I use a Matrikx + c2o filter garenteed not to leach phos for 3600 gallons. thgen dont over feed and your good. for extra measure add a fuge and your set
IMO Rowaphos is a better option. It is a phosphate binder and not just a sponge. It will not leach anything back into the water like some phos treatment materials.