HA! That's exactly what I need one for Tunze + GEO kalk reactor. I guess I'll give it a try. I have another question. Are you using the GEO kalk reactor or something else? If you're using the GEO, did you have to put a flow control on the line or something? The Tunze pump seems a bit too powerful and it ends up stirring the kalk up and dumping it my tank.