Do not feed the Kalk reactor with tank water. The high pH in the reactor will essentially precipitate everything from the salt water. Kalk reactor use RO water input and output use to top off water and your tank water evaporates.reefphreak":2f65rb3n said:Its on the input side. I feed the reactor with a small pump from the sump. the reactor level is above the sump level so when the pump is off (its timed reverse photo period) the water siphons out of the reactor.