No nitrates is a part of it to, what little you get is being taken by the green, I keep both and I find the red grows fast and stays bright red I have it under 5500k bulb and 10ppm nitrates zero phosphate. I have high flow through my sump. And its in with several other types of macro.
Without some sort of food the red will starve its not as Hardy as cheato or other green halimedas
