the new reactor i built for my tank is basically a single chamber reactor with a separate effluent chamber. i had to do it that way bc of space constraints. the 2nd chamber brings the effluent pH up to about 7 from 6.6 coming out of the first chamber. adding kalk helps keep the tank pH higher (i use a kalk reactor). when it is time to add new kalk to the reactor, my pH starts getting down around 8.