[ray-the-pilot]

Like most people I haven’t paid any attention to the level of chlorides in my tank. Last week just out of curiosity I checked a sample for chlorides using AgNO3 test solution. None were detected! This was really surprising since my tank is made up of 10 – 20% tap water and the remainder RO water. My city water has about 50 ppm chlorides: so my expectation was 5 ppm or more.

I made a 5 ppm chloride solution using KCl and tinkered with it. Clearly my city water produced way more precipitate than the 5ppm solution and my tank didn’t produce any. I diluted the 5ppm solution and estimated that my tank was probably less than 0.1 ppm chlorides.

I replaced 10% of my tank water with city water and rechecked the chloride level. It was slightly more than 5 ppm. The next day I recheck and found only a trace. I replaced another 10% of my tank water and found the Cl- to be over 5 ppm. The following day the level was below 5 ppm but over a trace. Now I check the Cl- every few days. It seems to be stable now between 5 and .5 ppm.

I didn’t notice any problems with plant growth in fact I would actually like my plant to grow slower.

One thing I did notice and posted this elsewhere was that my SAE’s were aggressively eating my plants. It may be they were making up for low salt levels in the water by eating more plants.

Now I’m wondering about the Na+ levels?

 

[ray-the-pilot]

Now here is an interesting paper that talks to the Cl- issue.

Now here is an interesting paper that talks to the Cl- issue.

http://www.inchem.org/documents/sids/sids/KCHLORIDE.pdf
You can weed through this but let me give you the salient point. The ration of K/Cl in dry weight plants is about 100/1. What that says is if your water is at 10 - 20 ppm K you need 0.1 - 0.2 ppm Cl- to be in the ballpark.

What does that mean to you?

Well, if you are using ordinary tap water you don't have to worry because the average concentration of Cl- in the US is 8 ppm.
If you are using RO water (like I am) then you need to check out the level of Cl-.

BTW the paper says that a deficiency in Cl- will result in a reduction of the plant surface area and eventually necrosis (death of tissue) might occur.
Now this is probably coincidence but the width of my sword plant leaves seems to have increased after adding more Cl-.

 

[ray-the-pilot]

Interesting Ray,
You are lucky that you have all of these test kits available. I think that using strictly RO water is a bad idea, we do not use fertilizers that are advanced enough to provide everything. EI and PPS count on the tap water providing a lot of nutrients. From this information i think we can start recommending you use RO to drop your KH to where you want, but not to use 100%.

Hey, thanks for the input. I agree, 100% pure RO water is not the way to go. That is why I was using 10 - 20% tap water with my RO water. I probably didn't say that clear enough.

With 10 - 20 % tap water and my tap water at 50 ppm; my chlorides should have been around 5 ppm or more. I was checking the kH, Ca and Mg levels and was sure that everything was at about the right level. When I checked the Cl- level, I was only doing it as a double check (a verification of my premise).

To find nothing was a big surprise!

My feeling is that Cl- is a more critical measure of the level of micronutrient requirements in a low GH/kH environment when you are using a tap water/RO water system.