Help with auto top off

Alright guys, I just got my sump tank plumbed in and the flow balanced. Now I need to build a system for auto-top off. In my mind I'd like to incorporate a kalkwasser reactor so overall I have a little less maintenance, But I have no space under my stand. That being said there is plenty of room in the basement under the tank. I've looked at a few threads on DIY reactors, but not too much at the differences. I'm thinking that I should do a RO system feeding the reactor tied to a float switch in the sump to monitor the water level.



Looking forward to the input. TIA