Thanks for the reply...

Ok, there is not much surface agitation, a 300pa Eheim pump is on the left of the tank positioned approx half way up the tank, it purpose to push the diffused CO2 around the mid back of the plants. The spray bar is at the top left and points diagonally (45dg) down towards the bottom of the tank. Are you suggesting surface agitation 24hrs?

Being low light, I'm dosing 2 x weekly 5ppm of KNO3 and 2 x weekly 5ml Flourish trace. Substrate is made up of laterite, Tetrapro complete and JBL floropol. When I see nitrates going up I dose 5ppm of K2SO4 - no K2HPO4 is added

I've read lots of threads on EI however cannot find any for the position I'm in with lighting etc... Any input would be great!