Kalkwasser problem

[Treebeard]

I dilute kalk in my ATO tub which is gravity fed into my sump. A float valve maintains a constant level in the sump. The problem is, the kalkwasser causes a surface scum in the aquarium with tentacle-like strands hanging below the surface, really quite ugly! It also clogs up the filter socks and they need to be replaced much too often. Just wondering if anyone else has had similar problems?