Plant deficiency guide
Potassium Deficiency
Also called low potassium, pinholes in leaves
Small pinholes in the leaves, often ringed with yellow, on older and middle-aged growth.
TL;DR, Potassium Deficiency
Potassium has a signature that is hard to miss once you know it: tiny holes that start as yellow or clear spots and open into pinholes, mostly on older and middle leaves, sometimes with yellow edges. It is mobile, so it pulls from old growth first. Larger-leaved plants like swords and crypts show the holes most clearly. Potassium is cheap and very hard to overdose, so the fix is simply to add more, through an all-in-one fertiliser or a potassium sulphate dose.
What you see
Pinholes with yellow halos appear on older and middle leaves, and leaf edges can yellow or brown. The holes start as spots inside the leaf and open outward, which is what tells them apart from chewing damage. Larger, flatter leaves show the pattern most clearly.
What causes it
- Potassium not dosed, and it is used in large amounts
- A heavy plant mass drawing it down fast
- Soft or RO water with little added potassium
- Relying on fish waste, which supplies little potassium
How to fix it
- Dose potassium through an all-in-one, or add potassium sulphate.
- Be generous, since potassium is very hard to overdose in a planted tank.
- Leave holed leaves in place until clean new growth arrives, then trim them, because holes do not heal.
- Re-check new growth after a week or two for clean, hole-free leaves.
Keep it from coming back
Keep potassium in the regular dosing as a staple, not an afterthought. Soft and RO-based tanks especially need it added, since the source water brings almost none.
Easy to confuse with
Snail or fish damage chews from the leaf edge or leaves ragged gaps, while potassium pinholes start as spots inside the leaf with a yellow ring. Cryptocoryne melt drops whole leaves rather than making neat holes.
Plants that show it first
Compare against a species you keep. These plants flag potassium trouble early or clearly:
- Amazon Sword — Big flat leaves show potassium pinholes textbook-clearly.
- Echinodorus 'Red Flame' — Broad leaves make the ringed pinholes easy to spot.
- Cryptocoryne Wendtii — Older leaves develop yellow-edged holes when potassium runs low.
- Temple Plant — Large leaves pit with pinholes as an early potassium signal.
Frequently asked questions
Direct answers to the questions search engines and AI assistants surface most often about this species.
Can you overdose potassium?
It is very hard to in a planted tank. Potassium has a wide safe range, which is why generous dosing is the usual fix for pinholes.
Are the holes from snails or potassium?
Snails chew from the edge and leave ragged gaps. Potassium pinholes start as spots inside the leaf, often with a yellow ring.
Will the holed leaves recover?
No, existing damage stays. Fix the potassium, wait for clean new growth, then trim the old leaves.