BRS high capacity GFO has always worked very well for me, I run it in a two little fishies 150 reactor without issue.
Kalkwasser is not a phosphate media
Kalk raises Phos?? That's not good.. I just oredered some to raise my ph..
First off kalkwasser is not a media! And kalkwasser precipitates phosphate, so I don't know where you got that from?
I used BRS high capacity GFO as well, but I got tired of it clumping up. Never could get the flow through it quite right. Recently switched to Cobalt's anti-phosphate resin. Still testing it and the anti-nitrate resin out, but at this time I'm atleast convinced they are pretty equal in terms of efficiency. And if that is the case, and it continues long term, then I'd tank resin in a bag over clumpy media any day. The experiment continues.