These are new leaves on a Microsorum pteropus 'Narrow'. Sorry for the grainy image - had to photograph from above, and they are only 2cm long. Note translucent leaf tips, yellow leaf and green veins. In the same tank I have two types of Vallais growing well and producing daughters (although one is pushing out some "crinkly" leaves), Echinodorus tenellus sending out runners and Java moss going nicely. Tank 25L 40x25x25 Light - 13W compact flourescent (desk lamp style, so light most intense over centre where this fern is). Filtration - 250L/hour HOB, cartridge replaced with ceramic noodles and filter wool. Dosing 140% dose daily of Easylife traces CO2 - none but 100% daily dose Easylife EasyCarbon No nitrate dosing except by the 2 adult and 20 baby guppies inside. Substrate - quartz gravel (I knew no better when I set this up). GH 9, KH 8, PH 7.8, Nitrates 0. I'm assuming either nitrate or CO2 is the issue but if someone has seen this before and can save me the trial and error so much the better.