Hi, I'm running a 240L (65Gallon) tank with 90L sump. Lighting cycle approx 9 hours per day. Aqua One skimmer, Phosban phosphate reactor, UV steriliser. Sump has cheatomorph and caulerpa (mainly Chaeto) growing well. Parameters are good - NO2 @ zero, NO3 @ zero, Ammonia zero, pH 8.3, trace phosphates only. My problem is that I can't get rid of red slime algae growing in the sump (cyanobacteria?). I manually remove as much of the stuff as I can and I trim back the chaeto to remove it where it's growing in the weeds but still it comes back and is a bit of a mess. Any ideas how to shift it? The only thought I had is that the light I use above the sump runs 24hrs/day - when I set up the tank I was told the chaeto/caulerpa would need light full-time. Is this correct? Thanks for your help.