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Nutrient Tunnel Vision

November 15, 2022 11 min read

Nutrient Tunnel Vision

Nutrient tunnel vision is pervasive in this hobby

In planted circles, aquarists quickly learn that nutrient dosing is important. And it is. However, many fall prey to the tendency to over extend this fact to see every change (or non-change) in growth/ form / color as solely linked to nutrients, and overwhelmingly in terms of some deficiency or imbalance.

This is partially due to availability bias: on public forums, list any plant defect and one invariably gets a ton of well-intended responses that focus on the nutrients that are presumably lacking. Forums are the number 1 spot for availability bias and group thinking, and it is easy to blame nutrients for plant problems. However, plants are affected by a huge number of non-nutrient related issues that can lead to yellowing/stunted leaves. When folks think that it is nutrient related - especially when they are already dosing adequate amounts, then they keep looking for wrong causation, which cause them to never solve their problems.

​The result is often a never ending circle of tweaking NPK and Iron dosing values, hoping to find the 'secret ratio' that finally gives the desired quality of plant growth as well as the complete disappearance of all algae issues. But no amount of fertilizer or water parameter tweaking alone will give a great tank as those are far from the only things that impact tank outcomes. We have seen experienced aquarists spend years running around the same circle, hoping to find some magic combination in their dosing ratios - they end up as somewhat better chemists, but their tanks look no better.

2Hr tanks often measure much lower nutrient values than people expect. Nitrate/NO3 levels in our water columns often bottom out or sit below 5ppm. This does not mean that the plants are under-fed; it just means that the residual level in the water column is low. Folks often mistake residual water column levels for what is available to the plants.

the deficiency in deficiency charts

Nutrient tunnel vision also stems from the widespread use of 'deficiency charts' which tend to oversimplify the cause, and over-focus on nutrients. See what the industry experts say:

"It is a chronic newbie-intermediate urge to get focused on deficiencies, even when they're following EI (!!). I used to think all my issues were lack of something or another and when you find charts like this, it temporarily confirms existing biases. You figure your issue is K deficiency. You add K2SO4 but nothing gets better. Then what? Then it's time to focus on other stuff. I've found many clever ways to kill and stunt plants, especially Rotala and Ammannia. Deficiencies are low down on the list. Poor maintenance and poor CO2 are big reasons." - Vin Kutty

"Grow the plants, not the deficiencies. The method is deceptive as it is simple."
​- Tom barr

The worst thing about this particular chart is that the picture for magnesium deficiency is wrong. The correct depiction of Mg deficiency is actually the opposite; pale/whitish veins coupled with green leaves.

Do I have nutrient tunnel vision?

"​I find it hard to name a factor besides Nutrients & CO2 that can cause changes to plant growth form or algae."
 "​I spend more time talking about my water parameters on online forums, than working on my tanks... What do you mean by working on my tank?" "​I have experimented with 1001 ways of dosing; different ratios, types of iron chelates, trace mixes, and yet my plants are no better than folks that just seem to follow simple fert regimes."


If those 3 statements resonate with you, you are not alone, as most hobbyists easily fall into the trap of nutrient tunnel vision.

The reality is that nutrient dosing, while important, is only one part of having good plant growth and an algae free tank. Tank results are largely dependent on other human-related maintenance factors that have nothing to do with nutrients or water parameters.

The nutrient dosing approach for our own tanks are almost absurdly simple. We dose a standard dosage of APT complete, and enrich the soil periodically - yet we can grow any commercially available variety of aquatic plant - and often grow it better than most folks. This is largely because we spend less time shadow boxing imaginary nutrient issues, more time on improving horticulture skills.

Ruling out deficiencies? - easy

Nutrient deficiencies are hard to spot accurately but actually pretty easy to rule out.

The easiest approach is to check that you have met the baseline values for the main nutrients to start with. The nutrient dosing page covers a variety of methods of how this can be achieved and what levels are reasonable. These levels have been tested by expert aquarists over the years and most tanks fall within the ranges.

It takes quite a sustained lack of a specific nutrient to induce an actual deficiency.

Find out what is in your tap water (details on understanding water parameters here) and find a regular method of dosing fertilizers. If you have followed the baseline ranges detailed in the nutrient dosing guide - it is actually pretty difficult to get deficiency symptoms for most tank setups. You will never see the deep deficiency symptoms detailed in "plant deficiency charts". For most plants, if a certain nutrient is present but in small amounts, the plant merely down-regulates growth to compensate.​

Aquatic plants would not survive long in nature if it required them to be constantly marinated in a highly concentrated fertilizer mix - most natural waters are very lean nutrient-wise compared to the levels we use in our tanks. The popularity of soil bases in modern aquariums, similar to in nature, also forms a backup reserve on which plants can draw from.

There are approaches to move from nutrient levels from a state of "nutrient sufficiency" to more "optimal levels" to get better form/color/health, these will be covered in later newsletters. For the purposes of avoiding efficiencies for 98% of the tanks out there, the above method will be more than adequate.

The major non-nutrient factor that causes more issues than anything else

Tom barr cites CO2 as the number 1 cause of plant issues by far - because it is difficult to check, many folks just assume levels are good because they seem to be injecting "a lot". In reality, depending on injection methodology, tank dimensions, flow setup and other factors, CO2 saturation rates can vary tremendously.

50% of plant mass is carbon while the most used "nutrient", Nitrogen, only makes up only about 1.5% of plant mass. Yet most hobbyists only have poor estimates of what their actual CO2 levels are. The same hobbyist can argue all day whether 15 parts per million NO3 is better or 20 parts per million NO3 is better. CO2 assimilation is light dependent; and plants can't utilize stored reserves (which they can do with NPK). NPK is commonly available through fish/soil/tap water, whereas CO2 has to be introduced, circulated, and degases naturally if injection is stopped while other minerals accumulate.

HC Cuba

HC is a pretty good indicator of CO2 levels near the substrate zone. It works much more reliably than any drop checker.

How to improve CO2 levels

Key steps in improving CO2 levels:

  1. Develop better methods of gauging CO2 levels. Learn the 1 degree pH drop method at least (drop checkers and BPS are NOT good gauges of CO2 levels). In the long run, learn to gauge levels by observing plant growth forms.
  2. Understand the importance of gaseous exchangein CO2 optimization. Does the flow pattern in your tank circulate surface layers of water (that contacts air) with deeper layers in the tank?
  3. Are you hitting peak CO2 before your light window comes on? If you are only hitting peak saturation late day, tank levels may be poor for the initial part of the day. Do not assume that starting CO2 injection one hour early means that you hit peak saturation by the time light comes on. For many setups, depending on injection methodology, it can take 2 to 5 hours to hit saturation.
  4. Do not assume that just because fish are gasping, that it means you have good CO2 levels in the water. The tank can simultaneously suffer from poor CO2 levels at one point, and excessive CO2 levels at another point in the day. Tanks with poor gaseous exchange tends to suffer from this dilemma. This is covered on the page on gaseous exchange as well.

Mistaking plant adaptation responses for 'nutrient deficiencies'

When the environment changes for a plant, there will be a period of adaptation as the plant reprograms its cells to optimize resources available in the new environment. When light becomes insufficient for example, we see stem plants channel energy into growing longer stems in order to reach the light. Many other changes occur at the cellular levels that are not so visible to aquarists. However, this often manifest as a deterioration of older leaves as the plant channels energy to new growth - new growth that is optimized to the new environment. New growth that is optimized for environment is robust and more resilient towards algae as well, while the older deteriorating leaves can develop algae.

There are two important angles to this. The first is that you should keep the overall environment of the tank stable, so that the plant does not keep re-programming its cells to match what is available. This means keeping CO2, water parameters and other nutrient variables consistent. New hobbyists in search of the holy grail of parameters often fail at this because they keep changing parameters before plants have time to adapt. Plants can take up to 2 to 3 weeks in faster growth systems to adapt fully to regime changes. While in slower growth systems or slower species (such as Bucephalandra), adaptation can take up to a couple of months to fully play out.

The second is knowing that old leaves on plants do not heal - this is so even if your 'new environment' has better variables than the old. If plants are adapting to new tank conditions well, new growth should be well colored and algae free but old growth will deteriorate and eventually you need to cut and replant the new portions of the plant, discarding the older deteriorating portions. The bigger the changes in environmental variables, the more plants have to adapt and the faster they will discard older leaves as cells there are not optimized for the current environment. Unlike humans that can heal, plants adapt by constantly growing new leaves and discarding older, less optimized growth. You can read more about maintaining old leaves here.

If you aim at preserving the maximum number of older leaves on a plant in the long run - keep the environment stable so that there are no adaptation changes.

It is not common to see large patches of sensitive plants like Hygrophila sp. Chai in hobbyists tanks. Most folks run their tanks in an unstable manner, which leads to premature deterioration of the older leaves. So although their Chai patch produces new leaves, it is countered by the degradation of older growth - thus the patch remains sparse. For plants such as these, they are a great test of long term stability of the tank.

Non nutrient, non-CO2 aspects of tank upkeep to consider:


  • Are plants overcrowded? Can the particular plant you are growing take some overcrowding or not?
  • Is there a lot of old growth that needs to be removed - is old growth blocking light and flow? - trim tops and discard bottoms.
  • Are aggressive growers shading and crowding out slower, more delicate growing plants - do adjacent plants block light & flow?
  • Do the growth tips have space to expand to?
  • Are you uprooting some plants too often (for species that are dependent on established root systems)?
  • Are you over trimming the plant; is it able to grow to the healthy height for that particular species?
  • Does the plant have space to grow to its full size before getting overcrowded?
  • Has the plant been given enough time to acclimatize to the tank? Was the original sample healthy to begin with?

Ludwigia sp red

Some plants such as Limnophila aromatica, Ludwigia sp red, and Myriophyllum 'Guyana' can be trimmed into neat bunches and tolerate slight over-crowding. Other plants may prefer more space to grow into good form. There isn't a blanket rule - but by observing the species in your own tank grow over time, its pretty easy to figure out.


  • Are all areas in the tank evenly lit ? If not, are some plants more shaded than they should be?
  • Areas adjacent to tall plants generally have significantly less light - light hungry plants may shaded indirectly.
  • Is self-shading an issue that leads to deteriorating old growth? Especially so for point source lighting & tall plants.
  • Colored plants - do your lights have the right spectrum profile to display them well?
  • Does the plant grow differently/better/worse in other light spectrums?
  • Is your hard scape blocking light at some angles?
  • How would it impact the plant if you doubled the light? Or halved it?

Shaded areas in a tank


  • Are the roots bright white when plant is uprooted (rather than mushy) ?
  • Do you vacuum away organic detritus away once in a while (please do) ?
  • Do you know if the particular plant you are having trouble with prefer fresh soil or matured soil ?
  • Does the quality of soil matter for the species of plant you are trying to grow ?
  • Is there an overly high build up of organic matter in the substrate ?
  • Is the soil compacted ? Does it matter for the specie you are growing ?
  • Is the soil nutrient levels depleted ? Does it matter for the species you are growing ?

Substrate zoom

Substrate is a useful tool for those who know how to manage it, a bane for those who do not. 


  • Does the flow reach plants that require it - do you know if a particular species prefers more flow or less ?
  • Most tank have some dead spots - do you have a strategy of managing yours?
  • Does your tank's flow pattern circulate the surface layer of water with deeper layers to get good gaseous exchange/O2 levels ?
  • Is your tank's bio-filtration matured and stable enough to maintain good water quality ?
  • Is organic waste being processed fast enough to avoid algae and water quality issues ?
  • Are you doing actions that cause our tank's water chemistry to fluctuate wildly - and do you know how to tell if this is happening ?

Oxygenation is as important for planted tanks as carbon dioxide. A successful planted tank is build upon an aggregation of small optimizations and effective choices.


Algae is a symptom, not just something to get rid of- Dennis Wong

If you have algae attached to plants, it indicates that the plant is under some sort of adaptation stress / not growing well. The question to ask is how to improve the health of that particular plant - removal of algae is a secondary concern. Folks often overly focus on tank parameters, but miss direct signals from the plants such as this.

Water changes are not enough - clear up detritus by siphoning if you do not want algae. Perfect parameters alone do not make an algae free tank.

These Bucephalandra planted on taller rocks receive around 300 umols of PAR, so its a myth that slower growers will get algae infested just because they are grown in high light tank. Overall plant health and tank cleanliness is a larger factor at play. 


Adopt a robust nutrient dosing regime in your tank, but once you have that, spend time in working on the other aspects of tank upkeep. Horticulture skill requires practice, experimentation and observation; and the upkeep of planted tanks is so much more than hitting specific water parameter numbers.

Though there are numerous angles to look at things - most of it boils down to observation of plant, fish and other happenings in the tank environment. Plants and livestock often give pretty direct feedback as to what is happening in the tank and changes to tank water quality.

​Hopefully, this article has shown a glimpse of the multitude of other factors that one can consider when analyzing plant issues.