I have a reactor for kalk, but Im currently just mixing it in my top off bucket. Ive used it both ways with good results. Years ago, my uncle had a 75 gallon he would dump a gallon of kalk water top off at a time. I would cringe at him doing it that way, but he never had a problem with it. I would add kalk water slowly with top off. If you use a float valve, and send kalk through the float valve, it WILL gum up and fail eventually. Kalk water builds up and likes to clog. good stuff, just keep an eye on it.