Chloride As A Macro Nutrient...? Myth???


New Member
Oct 14, 2018
Maryland USA
So first let me start off saying that on certain forums many members are bouncing around the idea that having potassium chloride or calcium chloride dosed will provide chloride as a macro nutrient, even to the extent of a recommended ppm of 5-20... The claim is it helps move nutrients around the plant.

Last I checked it just allows you to dissolve the ferts/gh booster better and faster, but is less beneficial due to many other reasons. From my deep search if the web I believe I found the rumor started up because seachem uses them in their liquid ferts, for dissolvability and stability reasons, and someone's mind thought it was there for another purpose. I read some about calcium chloride having a different effect on ph, making it more alkaline, but isnt that not ideal for a planted aquarium?

I'm not a chemist, nor am I super smart, this kind of stuff is very complex and many chemical reactions can occur in the aquarium that can change all that logic, such as reacting with a micro nutrient like iron or something. Some report that calcium chloride tends to make films that algae grows on like crazy, but that's not easy to prove.

So really what I am to believe? SeaChem is pretty good at getting solid responses to questions like this so I may get a response from them and post it here too.

I understand this is a forum, people will come forward with their hard beliefs, but hopefully some clarification can be achieved as forum rumors told as absolute truths can be misleading and downright harmful when someone applies the wrong info into their own aquarium.


Aug 23, 2018
So really what I am to believe?

First, you will probably collect many familiar opinions, as many of us cross-contaminate both this forum and TPT.

Your question: “So really what I am to believe?” is going to have to be something only you can answer. There are only anecdotal reports on chloride effects on plants in our hobby. Some report they’ve noticed issues in chloride-sensitive plants above 20ppm, some say 100 ppm and others report no problems at 200-300 ppm. Some use RO water and add no Cl-.

Most ‘scientific’ studies we will find on just about anything plant related, including chloride, are based upon terrestrial plants and, while there is a great deal of crossover, aquatic plants do have a lot of differences. Chloride is known to be necessary, for several reasons, in terrestrial plants.

Julia Adkins
Lifetime Member
Jun 22, 2015
Napa, California
The primary roles of chloride include:
  • Chloride is important in the opening and closing of stomata. The role of the chloride anion (Cl-) is essential to chemically balance the potassium ion (K+) concentration that increases in the guard cells during the opening and closing of stomata.
  • Chloride also functions in photosynthesis, specifically in the water-splitting system.
  • Chloride functions in cation balance and transport within the plant.
  • Chloride diminishes the effects of fungal infections in an as-yet-undefined way.
  • Chloride competes with nitrate uptake, tending to promote the use of ammonium nitrogen. Lowering nitrate uptake may be a factor in chloride’s role in disease suppression since high plant nitrates have been associated with disease severity.
Chloride is a critical component in the development of plants. Terrestrial plants do not have significantly different needs than aquatic plants. All living things have essentially the same nutritional needs. The difference lies in how different species digest and absorb those nutrients.


Aug 23, 2018
I agree that there are, probably, significant shared characteristics between terrestrial and aquatic plants, but there is such an absence of studies that it is hard to know to what degree any particular aspect applies to both. For example: aquatic plants generally do not have stomata, which negates being able to apply one of the known benefits of chloride in terrestrial plants, for aquatic plants.


Aug 12, 2017
I’m perplexed that Chloride, along with Sodium, are not one of 13 macro and micro nutrients Plants need. Sodium chloride is the most common electrolytes in all animal, and I can’t understand why plants lack and have no need for it. In a fishless tank with no source of NaCl from fish food, one can theoretically grow healthy plants with EI RO water, zero NaCl, right? Is it the reason why all herbivorous mammal need to eat mud to supplement NaCl that is lacking in plants?