if you plan on syatying in the hobby long term i would get one. best investment i have ever made. do not have to worry about dosing or anything at all. I do monitor the PH VIA controller in the event of the PH controller going out of wack in the reactor but other than it is set it and for get it. i purchased a GEO 818 and loaded it full. I know i wont have to worry about refilling it for at least 2 years. I purchased a large CA Rx because i plan on upgrading to a large growout/fish room