I'm going to be making a batch of James' DIY TPN+ this weekend. Now the current view on TPN+ is that it's a good all round fertiliser but that it works best for people who have high phosphates in their tap water. I looked at the water report for my area (PDF) but couldn't see any mention of phosphates at all. However I am suffering from quite a bit of GSA which I'm lead to believe is linked to PO4 deficiency. I'm currently dosing 5ml of TPN+ and 2.5ml of EasyCarbo a day on a 70l tank with DIY CO2. I have 45w T8 lighting split into 15w dawn/dusk and 45w full light. Dawn - Dusk ~10hrs and full light for ~8hrs. I change minimum 30l a week. Would it be worth increasing the PO4 in the DIY TPN+ I'm making this weekend and if so by how much and what's the easiest way of doing it. Increase the Potassium Phosphate to about 4g?