Kalkwasser problem
 

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?

I used kalk for many years using that method and never had issues with it.

yeah, i'd say that is abnormal too.

is the surface scum etc, in the sump where the kalk is dispensed via the float valve, or is it in the display tank?

if its in the display tank, perhaps you need to increase surface agitation.

add another powerhead...
or point one upwards to create more turbulence...
reposition your return line to create more surface agitation...

The scum is in the display tank. I disperse it by pointing a power head at the surface. But filter socks that used to last for days without changing are now plugging up in one day.
I got fed-up with it today and dumped the ATO water down the drain and refilling it with pure water.