[ytro]

Just my 2 cents - Your po4 level is pretty high compared to your no3. I know the 'golden ratio' is 10:1 (no3 to po4). It may be that your po4 may be driving your iron too low? Personally, I would try increasing no3 and decrease the po4. Something to like 10ppm no3 and 1ppm po4. I've always had success with S. Repens @ those levels in my tanks. BTW - I realize that you have some red stem plants and may be purposely low dosing no3 to bring out the red.

 

[ytro]

Just knew about it. Could you share some references telling that the wrong ratio may lead to Iron absorption issue?

Is it just PO4 with NO3 or N in general?

I guess I have to reduce the PO4 to 1:1 at least. And use root tabs

Just knew about it. Could you share some references telling that the wrong ratio may lead to Iron absorption issue?

Is it just PO4 with NO3 or N in general?

I guess I have to reduce the PO4 to 1:1 at least. And use root tabs

The name of the chart I referenced is called 'Mulder's Chart' (just google it). It will tell you how different nutrients effect one another. It shows that P and Fe have an antagonistic relationship.

Also, the golden ratio (10:1) I referenced is also known as the 'Redfield Ratio'. Try looking into that too.