just be careful . Just because its a fish store doesn't mean its going to be consistent . you are relying on someone else . What water do they use , what salt mix , did they change to a different brand of salt. how long has it been since they changed the RODI filters. what salinity do they mix the salt to , is it the same salinity every time . go to bulk reef supply web site , check out their RODI UNITS. they sell entire kits that mount to a sink . everything you need to install and operate . buy a refractometer not a hydrometer, your favorite salt mix and do it yourself . that's the only way you know your getting consistency.