Plant deficiency guide
Nitrogen Deficiency
Also called low nitrate, nitrate deficiency
Older, lower leaves fade to pale yellow evenly and go see-through, while the tips stay green.
TL;DR, Nitrogen Deficiency
Nitrogen is mobile, so a plant robs its old leaves to feed new growth when it runs short. The lower, older leaves turn uniformly pale yellow and then translucent while the new tips stay green. Fast-growing stems show it first. It usually means nitrate has bottomed out, often in a lightly stocked tank with no dosing. Add nitrogen through an all-in-one fertiliser or a nitrate dose, and feed a little more as the plant mass grows. In a few plants a mild shortage deepens reds, which is why some aquascapers run nitrogen lean on purpose.
What you see
The oldest leaves, lowest on the stem or oldest in a rosette, lose colour evenly across the whole leaf rather than between the veins. Pale green becomes yellow, then the leaf thins to translucent and rots away. New growth at the top stays green because the plant is moving its nitrogen up there. Overall growth slows and stems look leggy.
What causes it
- Nitrate has dropped close to zero, common in lightly stocked tanks with no dosing
- A heavy, fast-growing plant mass using more than the tank supplies
- Large or frequent water changes stripping nitrate faster than it rebuilds
- A new tank, before the fish load and feeding have caught up
How to fix it
- Test nitrate. If it sits at or near zero, that confirms it.
- Dose nitrogen. An all-in-one fertiliser is the simplest route, or dose potassium nitrate to bring nitrate into the 10 to 20 ppm range.
- Feed the fish a little more, since fish waste is a real nitrogen source in low-tech tanks.
- Trim the worst old leaves once clean new growth is coming in.
- Re-test after a week and adjust to hold a steady low level rather than chasing zero.
Keep it from coming back
Dose to keep nitrate in a steady range rather than letting it hit zero between water changes, and raise the dose as the plants fill in. In a low-tech tank, a sensible fish load and regular feeding often supplies enough on its own.
Easy to confuse with
Magnesium also hits older leaves, but it yellows between the veins and leaves the veins green, while nitrogen fades the whole leaf evenly. Potassium shows as pinholes rather than a smooth fade.
Plants that show it first
Compare against a species you keep. These plants flag nitrogen trouble early or clearly:
- Rotala Rotundifolia — A fast stem that pales from the lower leaves up as soon as nitrate runs short, so it works as an early warning.
- Water Wisteria — Hungry and fast, its lower leaves yellow and drop quickly when nitrogen is low.
- Dwarf Hygrophila — A fast grower whose older leaves fade first, easy to read as a nitrogen gauge.
- Ludwigia 'Super Red' — Runs deeper red under lean nitrogen, the flip side some aquascapers use on purpose.
Frequently asked questions
Direct answers to the questions search engines and AI assistants surface most often about this species.
How much nitrate should a planted tank have?
A common target is around 10 to 20 ppm for a tank with active growth. The exact number matters less than keeping it steady rather than swinging to zero.
Can too little nitrogen make my plants redder?
Yes, in some species. Running nitrogen lean shifts the balance toward red pigments, which is a deliberate technique. Push it too far and you get pale, dying old leaves instead of colour.
My new leaves are green but the old ones are yellow, is that nitrogen?
Very likely, if the yellowing is even across the whole old leaf. Nitrogen is mobile, so the plant sacrifices old leaves first.
Will a water change fix it?
No, water changes usually lower nitrate. The fix is to add nitrogen and then hold a steady level.