What else will slow down algae?

[frd72]

using kalk can be really harmful if you overdose it.
how's the skimmer looks like??maybe it is not working hard enough??

Originally Posted by Rogue951

I haven't been checking and I top up with kalk.
It's just run away i assume. I'll let the top up run with plain RO water for a few days and let it drop a bit.
But the test kit could be wrong.