I use a 44 gal brute can from home depot. Mix in 2 cups of kalk . The reefiller pumps are adjustable depending on your evaporation rates. My tank is a 180 so i chose not to use a float switch. I simply use a timer having the kalk go in overnight. It has kept the ph balanced which has improved the tank quite a bit. The 44 gals lasts a couple of weeks, before you reefill. It is basically idiot proof, no chance of float switches failing or over dosing. You can find more info in the chemistry forum. I have been doing this for a couple of years now and still have not cleaned the bottom of the can. Pretty sure Farley mentions a possible benefit form the residue left over.