The tank has been running about 12 weeks,6 of those doing a fishless cycle,the fish are already in the tank so dont think i can crank the co2 up any more,i did have a phosphate remover in the external filter but removed it yesterday on the advice from clive,ive had the drop checker in several positions in the tank and i'm getting the same readings where ever its placed. at present i'm changing 100ltrs of water every week,should i just carry on with the tpn+ til its all gone or after the next water change start with EI? I've just trimmed all the brown leaves off the plants so i suppose i'll just have to see how things go over the next couple of weeks,another problem i have is i cant drop the ph to low cause of the nerite snails.so 30ppm of co2 is not going to be acheivable. Clive suggests cutting the lighting by 50% does that mean just having the lights on for 4 hours instead of 8? if so will it still be ok to have the co2 running for 9 hrs,sorry for all these questions,i'm new to planted tanks and just want to get things right.