Nutrient Tunnel Vision

Nutrient tunnel vision is pervasive in this hobby

In planted circles, aquarists quickly learn that nutrient dosage is important. And it is. However, many fall prey to the tendency to exaggerate this fact and see any change in growth/shape/colour as solely related to nutrient availability.

In reality, there are many non-nutrient factors that affect plant growth form. For example, if you plant a light demanding plant in the shade of a larger plant, the lack of light will cause it to grow poorly no matter how much nutrient you give it. The same can be said for newly transplanted plants in a new environment. Such plants may take a few weeks to adapt to the new environment before their colouring improves. The plant needs time in such a scenario, not more nutrients.

A whole range of horticultural techniques, plant positioning and tank maintenance factors can affect plant growth. These factors often have a greater impact on plant growth than nutrient levels, but are rarely discussed.

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.

Do I have nutrient tunnel vision?

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.

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

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

50% of plant mass is carbon, while the most commonly used "nutrient", nitrogen, is only about 1.5% of plant mass. Yet most hobbyists have poor estimates of their actual CO2 levels. The same hobbyist can argue all day about whether 15 ppm NO3 or 20 ppm NO3 is better. CO2 assimilation is light dependent and plants can't use stored reserves (which they can with NPK). NPK is generally available through fish/soil/tap water, whereas CO2 has to be introduced, circulated and naturally degassed when injection is stopped, while other minerals accumulate.

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 measuring CO2 levels. Learn at least the 1 degree pH drop method (drop checkers and BPS are NOT good measures of CO2 levels). In the long term, learn to measure 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. Do you reach your CO2 peak before your light window comes on? If you are not reaching peak saturation until late in the day, tank levels may be poor for the first part of the day. Do not assume that starting CO2 injection an hour earlier means you will reach peak saturation by the time the light comes on. For many setups, depending on the injection method, it can take 2 to 5 hours to reach saturation.
4. Do not assume that just because fish are gasping that you have good CO2 levels in the water. The tank can suffer from low CO2 levels at one time and high CO2 levels at another time of the day. Tanks with poor gas exchange tend to suffer from this dilemma. This is also covered on the gas exchange page.

Non nutrient factors that greatly impact plant health

PLANT HUSBANDRY

• 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?

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.

LIGHT

• 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?

SUBSTRATE

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

Filtration and flow

• 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.

Confronting algae

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. 

The deficiency in deficiency charts

Nutrient tunnel vision also stems from the widespread use of 'deficiency charts', which tend to oversimplify the cause and focus too much on nutrients. See what industry experts have to 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 picture for Mg deficiency is actually the opposite; pale/white veins coupled with green leaves.

On public forums, list any plant defect and you will invariably get a ton of well-intentioned replies focusing on the nutrient that is supposedly lacking. Forums are the number one place for availability bias and often become an echo chamber for bad advice. The result is often a never-ending cycle of tinkering with NPK and iron levels in the hope of finding the 'secret ratio' that will finally produce the desired quality of plant growth, as well as the complete disappearance of all algae problems.

We have seen experienced aquarists run around in circles for years, hoping to find some magic combination in their dosage ratios - they end up being slightly better chemists, but their tanks look no better.

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 basic ranges detailed in the nutrient dosage guide - it is actually quite difficult to get deficiency symptoms for most tank setups. You will never see the deep deficiency symptoms detailed in the "Plant Deficiency Charts". For most plants, if a particular nutrient is present but in low levels, the plant will simply reduce its growth to compensate.

Aquatic plants would not survive long in nature if they had to be constantly marinated in a highly concentrated fertiliser mix - most natural waters are very nutrient poor compared to the levels we use in our tanks. The popularity of soil bases in modern aquariums, much like in nature, also provides a reserve from which plants can draw.

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

Rotala macrandra mini type 4 red. Its full form and intense colouration comes from a combination of good fertilisation, strong light and adequate space to grow.

Mistaking plant adaptation responses for 'nutrient deficiencies'

 When a plant's environment changes, there is a period of adaptation during which the plant reprograms its cells to optimise the resources available in the new environment. For example, when light becomes scarce, we see that stem plants divert energy into growing longer stems to reach the light. Many other changes occur at the cellular level that are less visible to aquarists. However, this often manifests itself in the deterioration of older leaves as the plant channels energy into new growth - new growth optimised for the new environment. New growth optimised for the environment is robust and more resistant to algae, whereas the older, decaying leaves can develop algae.

There are two important aspects to this. The first is to keep the overall environment of the tank stable so that the plant is not constantly reprogramming its cells to adapt to 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 because they keep changing parameters before the plants have had time to adapt. In faster growth systems, plants can take up to 2-3 weeks to fully adapt to regime changes. In slower growth systems or slower species (such as Bucephalandra) it can take up to a couple of months for adaptation to be complete.

The second is to know that old leaves on plants will not heal - this is true even if your 'new environment' has better variables than the old. If plants adapt well to new tank conditions, new growth should be well coloured and free of algae, but old growth will deteriorate and eventually you will need to cut and replant the new parts of the plant, discarding the older, deteriorating parts. The greater the changes in environmental variables, the more plants will have to adapt and the faster they will discard older leaves as their cells are not optimised for the current environment. 

Unlike humans, who can heal, plants adapt by constantly growing new leaves and discarding older, less optimised 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 delicate plants such as Hygrophila sp. Chai in hobbyist tanks. Most people run their tanks in an unstable way, which leads to premature decay of older leaves. So although their Chai patch will produce new leaves, this will be offset by the decomposition of older growth - leaving the patch sparse. For plants like this, they are a great test of the long-term stability of the tank.

Conclusion

Establish a robust nutrient dosing regime in your aquarium, but once you have that, spend time working on the other aspects of aquarium maintenance. Horticultural skill requires practice, experimentation and observation, and the maintenance of planted tanks is much more than hitting certain water parameters.

Although there are numerous angles from which to view things, most of it boils down to observing plants, fish and other events in the aquarium environment. Plants and animals often give fairly direct feedback as to what is happening in the tank and how the water quality is changing.

Hopefully this article has given a glimpse of the many other factors to consider when analysing plant problems.