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. Humans gravitate towards tools and concepts that come readily to mind, and forums are the number 1 spot for availability bias and group thinking. 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.
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 not even accurate.
"I find it hard to name a factor besides Nutrients & CO2 that can cause changes to plant growth form or algae."
|"I spend alot more time testing and tweaking NPK values than actually observing and working on the plants."||"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 commercially available fert regimes."|
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.
What most people are looking for is optimal growth - not just avoiding deficiencies.
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.
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 is a pretty good indicator of CO2 levels near the substrate zone. It works much more reliably than any drop checker.
Key steps in improving CO2 levels:
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.
Substrate is a useful tool for those who know how to manage it, a bane for those who do not.
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 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.
Many of the answers to the questions above are found on this website. Others can only be answered through specific experience with indicator plants (for example, HC is a great indicator for CO2 levels) - of which some are covered in the plant profile segments. Over time, this site and future newsletters will explore the various aspects of tank management.
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.