RO Perfect – pH Buffering, Cl- and Cal-Mag RO Water Primer for Hydroponic Systems


NPK 1 – 0 – 1

Includes Acetate Citrate pH Buffering System



Manic Botanix – Solid Logic, Pure Science


RO Perfect is formulated specifically for use with RO water, which requires priming with pH buffers, chloride and Cal-Mag to promote optimal growth.


Topics covered

About chloride

pH Buffers in hydroponic solutions: Overview

The problem with chemical pH Buffers


About RO Water

When filtering mains/tap water through a reverse osmosis system you are not only removing unwanted elements but also removing some wanted elements. For example, most hydroponic nutrient manufacturers formulate their products for tap water supplies, allowing for the fact that some random (?) amount of calcium and magnesium will be provided to the working solution beyond that which is provided by their nutrient. Other than this, you are removing alkalinity from the water which results in pH instability. In short, RO is pure water and pure water has no or very little pH buffering capacity. Therefore, even a very tiny amount acid or base will cause the pH to swing from very low to very high, respectively.  Further, RO filtration removes chloride (Cl) from mains water and, as a result, the addition of Cl is necessary for optimal results.   Therefore, when using RO water it is necessary to prime it for use in hydroponics by; 1) adding some pH buffering; 2) adding ‘Cal Mag’ to the working solution to compensate for the calcium and magnesium that was removed during RO filtration and; 3) adding some Cl to solution.

This situation also applies to where rainwater is used. I.e. rainwater also needs Cal Mag, Cl and alkalinity added before use in your hydroponic system. View/compare lab analysis of mains/municipal and RO water. See following

Mains/municipal water test. Compton California Supply


RO Water lab analysis (origin of source water supply, Oakland California) 


The Science that Separates RO Perfect from the Cal-Mag Pack


RO Perfect is quite unique when compared to most hydroponic store sold Cal-Mag additives (which are typically just formulated using calcium and magnesium nitrate) in that RO Perfect is formulated with an acid and conjugate base pH buffering system


Additionally, RO Perfect is formulated in such a way that potassium (K)  are present at levels which aim to maintain an off-the-shelf hydroponic nutrient’s N to K ratios within optimal ranges. That is, often off-the-shelf additives can greatly change a hydroponic solution’s (nutrient + water) NPK ratio. For example, many Cal-Mag additives not only contribute Calcium (Ca) and Magnesium (Mg) to solution but they also add high levels of Nitrate Nitrogen (NO3 N) to solution. This means that when these Cal-Mag additives are applied to solution the nutrient in solution suddenly has a high, less than optimal NO3 N to K ratio, meaning that the all-important nutrient solution becomes imbalanced.


Thus, RO Perfect is formulated with the equivalent amount of K to N to maintain the solutions N to K ratio at optimal levels.


RO Perfect also adds very low levels of the microelements Fe, Mn and Zn to solution. Further, RO Perfect provides 30ppm of chloride (Cl-) to solution.


About Chloride


Where RO filtration is used, the addition of chloride to hydroponic solutions is critical because RO filtration removes most of the chloride from mains/municipal water. This needs to be corrected through the addition of chloride at levels that will promote optimal growth.


Chloride is an essential element for plants.  It is a component of common salt and found in seawater. It should not be confused with other forms of the element such as chlorine gas (highly toxic and unstable), chlorine in swimming pools, hypochlorite (a sterilant and bactericide), hydrochloric acid (corrosive and dangerous liquid) etc. Chloride (Cl -) is the negatively charged anion of chlorine, which is the form it is found in naturally. It is non-toxic and readily adsorbed by plants.


Chloride regulates the function of several enzymes, it is essential (working in tandem with potassium) to the proper function of the plants stomatal openings, thus controlling internal water balance. It functions in cation balance and transport within the plant and is essential for transport of the nutrients calcium, magnesium and potassium. Studies have shown that Cl- diminishes the effects of fungal infections in an as yet to be understood way, although this might be related to Cl- reducing N accumulation in plant tissue. That is, it is speculated that Cl- competes with nitrate uptake. This may be a factor in its role in disease suppression, since high plant nitrates have been associated with disease severity.


Until recently, the recommended concentration of Cl – ions in nutrient solutions for growing tomatoes in rockwool was 35 ppm in the applied solution and 70 ppm in the root zone. The latest reports suggest that proper fertilization of tomato plants requires chlorine concentrations of 50 ppm in the nutrient solution delivered to the plants and 100 ppm in their root zone, Because RO filtration removes most of the Cl- from mains treated water it becomes important to add some Cl- to RO water in order to correctly prime it for use in hydroponic growing. Some chloride (perhaps 2ppm) is invariably found in RO treated mains water and it is further present as a contaminant in fertilizers. In other cases, some off-the-shelf nutrients may contain chloride based fertilizers which contribute Cl- to solution. For example, House and Garden Coco nutrient contains reasonably high levels of Cl- and if you were applying too much Cl to solution through e.g. the use of RO Perfect and House and Garden Coco Nutrient this could result in too high levels of Cl in solution. Therefore, we (Manic Botanix) tend to take a fairly conservative approach and just add 30 ppm of Cl to solution via RO Perfect. That is, RO Perfect provides enough Cl- to promote optimal growth while not providing so much Cl- that it could have an adverse effect on growth when other sources of Cl- are factored into the nutrient solution equation.


Understanding pH Buffers 


A pH buffer is a substance that can be added to the hydroponic solution and that distributes itself as different ionic species that can react either with acids or with bases at certain pH levels. Put more simply, a pH buffer’s function is to provide reaction “alternatives” for strong acids and bases when they contact the nutrient solution. These acid or base substances generally react with water and this changes the value of the pH. When a buffer is present, they react with the buffering molecules instead of the water and the pH of the water, therefore, remains more stable than it otherwise would. Conceptually, a buffer acts somewhat like a large sponge. As more acid is added, the “sponge” absorbs the acid without changing the pH much. The “sponge’s” capacity is limited however; once the buffering capacity is used up, the pH changes more rapidly as acids are added.


The buffer is also available for your plants to uptake and therefore we are limited to chemical buffers which are non-toxic to plants and which allow us to control pH within a given range. Certain buffers such as MES (C6H13NO4S) offer good results although they are hard to access and are very expensive which is the reason why they are not widely used by hydroponic growers (MES is mainly used in biology and biochemistry and is typically only used in hydroponic research where precision, not cost, is the determinant factor). MES has a buffering range of pH 5.5- 6.7 which makes it suitable for pH buffering in hydroponic settings.


Other than MES, research has shown that nutrients themselves can be buffered further than the norm by diverging somewhat from traditional hydroponic formulation practices and instead formulating using KOH (potassium hydroxide) and H3PO4 (phosphoric acid) which acts to buffer pH through an HPO42-/ H2PO4 buffer system.[1]  However, Bugbee (2003) points out that phosphorus in solution buffers pH, but if phosphorus is maintained at levels that are adequate to stabilize pH (1 to 10 mM) it becomes toxic to plants.[2] Therefore, phosphate buffers have their limitations and need to be used in conjunction with other buffering agents in order to maintain buffering over extended periods of time.


Ultimately, however, unless you understand nutrient formulation/chemistry or are prepared to spend large sums of money on chemicals such as MES these approaches aren’t practical for most hydroponic enthusiasts.


A far cheaper and more practical way of buffering the hydroponic working solution is through the use of organic and inorganic components that have low toxicity to plants and are compatible to the nutrients used in hydroponics. Based on these parameters phosphates, carbonates, citrates, and acetates make reasonable buffers, with carbonates or bicarbonates such as potassium carbonate and/or sodium bicarbonate being the most practical choice. However, we are somewhat limited by their buffering capacity and by the concentration values that can be used. For this reason we cannot have unlimited buffering capacity when working with these components. Further, due caution is advised when working with these buffers because if overused, in the case of carbonates, too much alkalinity will exist in the nutrient working solution, reducing nutrient uptake. Further, carbonates can bond with calcium and magnesium in solution forming insoluble calcium and magnesium carbonate so we are limited to how much carbonate we can add to solution before it becomes detrimental.


That is…


Most growers would have heard of lime scale or hard water which is the result of water being high in calcium, magnesium, carbonate and hydrogen carbonate. This can result in the precipitation of calcium and magnesium carbonates in pipes and equipment in contact with the water.


Interestingly carbonate chemistry occurs in all natural waters including sea water and any water exposed to air. It is also the mechanism used in blood not only to transport CO2 back to the lungs in the form of carbonic acid, but is a part of what’s called the bicarbonate buffering system which is used to regulate the pH of your blood. The reason carbonates occur in natural waters is because carbon dioxide is soluble in water and the gas in the air in contact with water passively dissolves in water to form carbonic acid. The following chemical equation shows the relationship between the different carbon forms in water.




The arrows in both directions indicating that it is a reversible reaction with an equilibrium that can be shifted.

The concentration of each of these molecules increases or decreases with additions or reductions of one or the other, the change of temperature, pH and pressure. Without going into too much detail about what or how these shifts in concentration occur, you can now understand that these forms of carbon molecules will already be in the liquid nutrients you use. Also knowing that the fertilizers you use are reasonably high in concentrations of Ca and Mg and that this can lead to precipitates forming if carbonate levels in solution are too high.

This said, carbonates don’t instantaneously cause precipitation of these ions, but if too much is added to solution, precipitation will occur. Based on this, while additional carbonates may offer more pH buffering there comes a point where too much carbonate in solution will have negative outcomes. For this reason, growers should be cautious of adding too much CO3 to solution.

Additionally, where citrates (e.g. citric acid) are used, they can bond with calcium, forming insoluble calcium citrate which then precipitates (drops) from solution. Further, citrates act as food (carbohydrates) for microflora (both beneficial and pathogenic microorganisms) so when used in hydroponic systems they should be used with beneficial microorganisms (e.g. Trichoderma or Bacillus) for best results.


Conversely, oxidising agents such as monochloramine, hydrogen peroxide and chlorine should not be used in conjunction with organic components such as citric acid because chemical reactions occur between oxidising agents and organic components that can 1) render the oxidising agent inert and 2) change the molecular structure of the organic molecule. You can read more about these chemical reactions here….


It is important to note that carbonate and citric acid buffering provides only a very mild buffering action. If growers are looking for long term pH stability at a given pH in RO or mains water and they don’t wish to manually adjust pH using pH up or down, they then need to begin looking at chemical pH buffers that are designed for the purpose of maintaining pH within a narrow range for an extended period of time.  However, Manic Botanix does not recommend the use of chemical buffers because, for example, when discussing MES, while MES is shown to stabilize pH in hydroponic systems, studies have also shown that the presence of MES in the root zone solution can have adverse effects on growth/yields.[3]   

Chemical pH Buffers in Hydroponic Solutions – the Science  

In the research by Frick, J and Mitchell CA (1993) the authors tested MES buffer at 10mM and Amberlite DP-1 (cation-exchange resin beads). In the case of the Amberlite resin beads they were incorporated into a substrate mix of two parts vermiculite to one part perlite (v/v) growth medium at 6% or 12% of total substrate volume. Both strategies stabilized pH without toxic side effects on plants. The highest shoot harvest index (19.5%) occurred with the 6% resin bead treatment, even though the 10 mM MES and 12% bead treatments maintained pH within the narrowest limits. This research, therefore, indicates that although MES maintains optimum pH it also potentially impacts on growth.

In another study by Nicholas and Harper (2008) it was found that nitrate uptake by 27 to 29 day‐old soybean plants was significantly slower when solutions were buffered with MES than with IRC‐50 resin. Rate of nitrate uptake decreased with increasing MES buffer concentrations and decreasing pH in short‐term studies on plants previously grown on IRC‐50 resin buffered nutrient solution. Mass of the plants grown on IRC‐50 resin buffered nutrient solution equaled or exceeded that of plants grown on 1, 2, or 4 mM MES. Total elemental uptake (mg/plant) by plants grown on nutrient solution buffered by IRC‐50 resin, for the ten elements tested, was equal to or greater than uptake by plants grown on nutrient solution buffered by 1, 2, or 4 mM MES. It was concluded that IRC‐50 resin in recirculating hydroponic systems provides better pH control than does MES buffer for hydroponically grown soybean.[4]

In research, conducted on maize by Medeiros et al (1993) the authors concluded that MES “had marked effects on mineral nutrient uptake which should be considered when MES is used to control pH of nutrient solutions for growth of maize.” [5]

There are also some questions surrounding the suitability of MES for use in producing consumable crops. That is, when looking at the molecular structure of MES it contains a morpholine ring. Morpholine is a solvent and emulsifier that is commonly used in the preparation of wax coatings for fruits and vegetables, although morpholine’s use for this purpose is now banned in the EU because it is known to be a precursor of N-nitrosomorpholine (C4H8N2O2), a known carcinogen. Put simply, in the presence of excess nitrite (NO2−) morpholine can be chemically modified (nitrosated) to form N-nitrosomorpholine (NMOR), a genotoxic carcinogen in rodents. The WHO (1996) notes, “Morpholine does not appear to be mutagenic or carcinogenic in animals. However, it can be easily nitrosated to form NMOR, which is mutagenic and carcinogenic in several species of experimental animals. Morpholine fed to rats sequentially with nitrite caused an increase in tumours.” And: “Morpholine can undergo a variety of reactions. It behaves chemically as a secondary amine.  Under environmental and physiological conditions, the proven animal carcinogen N-nitrosomorpholine (NMOR) is formed by reaction of solutions of nitrite or gaseous nitrogen oxides with dilute solutions of morpholine.”[6]  

While Nnitrosomorpholine is unlikely to be taken up by plants, morpholine is shown to be systemic in morpholine based fungicides, so if present in solution it is available for uptake. Just one of these fungicides Tridemorph has been listed as a potential endocrine disrupter by the German Federal Environment Agency who report that it is linked to cystic ovaries. Tridemorph is an inhibitor of the human sterol isomerase enzyme which is part of the cholesterol biosynthesis pathway.


I should note that this is extremely complex chemistry and there are multitudes of factors involved (not the least of which is the mode of exposure and dose) that may influence proceedings and I expect any health risk associated to MES in solution is relatively low to absolutely minimal. This said, where my own growing practices are concerned I try to avoid the use of any potential contaminants that may remain residual in the harvested product. Thus, with the potential for chemical buffers to 1) reduce yields and 2) potentially contribute toxins to the end product Manic Botanix does not to recommend the use of chemical buffers in the production of consumable hydroponic crops.

RO Perfect Tech Data

ppm of nutrients in solution when used at full strength recommended usage rate of 0.6924 g/L or 6.924 g/10L

Total N  = 42.9ppm

N as NO3 N = 39ppm

N as NH4 N = 3.9ppm

Total P as elemental P = 8.544 ppm

Total P as P2O5 = 19.60 ppm

Total K as elemental K = 39 ppm

Total K as K2O = 47.00 ppm

Total Ca = 40 ppm

Total Mg = 20 ppm

Total Cl = 30 ppm

Total CO3 = 66 ppm

Total Fe = 0.2 ppm

Total Mn = 0.05 ppm

Total Zn = 0.025 ppm


NPK = 1 – 0.2 – 1

Ca to Mg ratio = 2:1

Total ppm of nutrients in solution = 172.133

CO3 not included in total ppm of nutrients = 66 ppm CO3

Total ppm with nutrients and CO3 = 238.133 ppm


Formula, lab analysis and tech data to be added shortly…..




[1] J. S. Saparamadu et al (2009) A low cost nutrient formulation with a buffer for simplified hydroponics systems

[2] Bugbee, B Nutrient Management in Recirculating Hydroponic Culture, presented at the South Pacific Soil-less Culture Conference, Feb. 11, 2003 in Palmerston North, New Zealand

[3] Frick, J and Mitchell C.A. (1993) Stabilization of pH in solid-matrix hydroponic systems. See also Joseph C. Nicholasa & James E. Harpe (2008) Effect of MES [2(N‐morpholino)ethanesulfonic acid] and amberlite IRC‐50 resin on nutrient pH control and soybean growth

[4] Joseph C. Nicholasa & James E. Harpe (2008) Effect of MES [2(N‐morpholino)ethanesulfonic acid] and amberlite IRC‐50 resin on nutrient pH control and soybean growth

[5] C. A. B. Medeiros et al (1993) Effects of mes [2(n‐morpholino)‐ethanesulfonic acid] and ph on mineral nutrient uptake by mycorrhizal and nonmycorrhizal maize

[6] International Program of Chemical Safety Report on Morpholine, World Health Organization, Geneva 1996 ISBN 92 4 157179 9