Two years with a GEO calcium reactor,first the good things about the reactor it works like george said it would ,i change the media every 6 mos and a new co2 one time a year.The PH will not go down at night it about 8.2 before the lights come on and i do not used kalkwasser to help keep the ph up .The only thing that to be change is a new lid because it would not seal . Would i buy one again yes. A good calcium reactor for the money.