Say hello to the new KNOP Calcium Reactor Compact 80. KNOP thought it was a good idea to design a Calcium Reactor that handles aquariums from 50-250 liters (13-66 gallons) and we would have to agree with them. This new Compact 80 is a great fit for nano aquariums which have increased in popularity over the years. This KNOP reactor is pretty simple, mount the calcium reactor, add your CO2 source and you’re all set. Although we are not exactly sure where you’re supposed to mount this, ideally your sump if you have one, but it sure looks like it could fit in the filter area if you have a nano aquarium with filters in the back. This is hitting Germany next week, with a suggested retail of 89 euro, or roughly $117.