http://www.bulkreefsupply.com/store/products/reactors/kalkwasser-reactor/aquamedic-kalkwasser-stirrer-reactor-1000.html Many of the other kalkwasser reactors available use a mixing pump to vigorously mix the kalkwasser at periodic junctions. This creates a highly concentrated slurry of kalkwasser that cannot be dosed until it has settled out. To protect against this danger, these types of reactors require a complicated series of timers to control pump operation. This series of timers ensures that the feed pump does not operate for at least one hour after the mixing pump stirs up the kalkwasser. This setup will fail if a timer fails or a setting is bumped which will lead to a disaster. This overdose danger with other stirrers is why the AquaMedic Kalkstirrers are BRS Recommended. Aquamedic Kalkwasser Stirrers feature a bar that slowly spins continuously to keep the kalkwasser saturated at the right level. It does not create the heavy kalk slurry common with competing brands. This simple feature eliminates much of the overdose risk.