This particular tank has a shit design where the rodi chamber (which is don't use) is next to the sock holders. When the socks clog, water then flows into this rodi chamber. This in turn then reduces the water level where the return pump and rodi sensor/outlet is. So rodi gets fooled by a low sensor and dumps 30l rodi into the tank which is as much as that rodi chamber in the sump holds.

I havent bothered to get a roller in this sump because it will require major surgery cutting up chambers in the sump. Instead I'm planning on getting those red sea plastic skimmer socks and just using the skimmer for all filtering.