Just got back from 3 weeks away. The CO2 ran out - don't know when, and the person who was supposed to be looking after the tank and dosing EI trapped his sciatic nerve so didn't dose or do the weekly 50% water changes On my return I was greeted by a tank looking like this one pictured on James' Planted Tank website: http://www.theplantedtank.co.uk/algae/rhizoclonium3.jpg I've removed as much as was practical by hand and changed 50% of the water. The HC carpet is smothered in the stuff, which I'm assuming is Rhizolonium from the pics details here http://www.theplantedtank.co.uk/ (thanks James!) I have changed the FE and started EI again. What do I need to do to rid the tank of this? Will a black-out affect Rhizoclonium? Thanks.