Aquatic plant deficiency

Deficiencies of water plants are often hard to diagnose because damaged leaves look very similar. Despite this fact, in this article we will try to describe the most important deficiencies.

CO2 deficiency is usually the biggest problem. You want to have level of CO2 20 – 30 ppm in your aquarium. Don’t underrate water flow. Try to aim for 10x or more the rated filter flow rate to tank size.

Mobile and immobile nutrients

If there is a lack of some kind of nutrient, plant can transfer this nutrient from older leaves to new leaves to preserve growth. Different nutrients can be transfered inside of the plant in different speed rates. We can divide these nutrients into two groups – mobile and immobile. “Slow” nutrients are called immobile. These types of nutrients aren’t able to get into new leves in time so deficiencies of these nutrients are shown on new leaves. In contrast, deficiencies of mobile nutrients are shown on older leaves.

Mobile nutrients: Nitrogen (N), phosphorus (P), potassium (K), magnesium (Mg), molybdenum (Mo)

Immobile nutrients: Iron (Fe), calcium (Ca), sulfur (S), boron (B)




Nitrogen – from nitrate (NO3), ammonia (NH4), urea

Optimal levels of nitrate (NO3): 10 – 40 ppm NO3

Water plant becomes yellow and older leaves are in a really bad condition.

New leaves are small and crippled. Growth rate of plants is very small.

Solution: Add some extra NO3 to you aquarium water from Potassium Nitrate (KNO3) – How much of nitrogen from KNO3



Phosphorus – from phosphate (PO4)

Optimal levels of phosphate (PO4): 0.2 – 3 ppm PO4

Water plants stop growing. Coloration is bad, plants are lighter. Older leaves are filled with Green Spot Algae (GSA). Generally, deficiency symptoms are similar to nitrogen deficiency symtoms.

Solution: Add some extra PO4 to you aquarium from Monopotassium Phosphate (KH2PO4) – How much of phosphorus from KH2PO4



Potassium (K)

Optimal levels of potassium (K): 5 – 40 ppm

There are formed tiny brown dots on older leaves. These dots are bordered partly yellowish. Dots becomes bigger.

New leaves are reduced in size. Plant becomes yellow.

Solution: Add some extra Potassium (K). You can use Potassium Nitrate (KNO3). If you have enough of nitrates (NO3), you can use Potassium Sulphate (K2SO4) instead – Read more about potassium fertilization



Iron (Fe)

Optimal levels of iron (Fe): 0.2 – 1 ppm

Iron deficiency appears on new leaves. Plants don’t have enough of chlorophyll in there so new leaves are pale.

The leaf tissue becomes pale usually faster than the leaf veins.

Iron deficiency can be observed on fast-growing plants firstly.

Solution: Add some extra micronutrients in form of Tenso Cocktail or CSM+B. You can also use liquid fertilizer (Seachem, Tropica, EasyLife…) How much of Tenso Cocktail should I use



Magnesium (Mg)

Optimal levels of magnesium (Mg): 5 – 10 ppm

Magnesium deficiency is usually similar to iron deficiency because lack of magnesium prevents to absorb iron.

All old and new leaves are thus pale, there is a strong chlorosis. In contrast to a potassium deficiency, veins of leaves remain the same. Chlorosis is only on the leaf tissue.

Solution: Just use Magnesium Sulfate Heptahydrate (MgSO4x7H2O). How much of MgSO4x7H2O should I use



Calcium, boron and other trace elements

Optimal levels of Calcium (Ca): 20 – 30 ppm

New leaves are pale. The leafe tissue is reduced but leafe veins remain ok.

Be aware of the fact, that usually there’s not problem with calcium, because Ca is present in tap water. But in case, that you are using extra soft water, you can have a problem.

Boron and other trace elements are contained in iron fertilizers such as Tenso Cocktail or CSM+B.

Solution: In case of the calcium deficiency, you can use Calcium Carbobate (CaCO3). Try to add some extra Tenso Cocktail and CSM+B in case of micronutrient deficiency. More about iron and trace elements