TDS question, help!!

[frenchy87128]

I grow my indoor collection in a large black container which I just fill with deionized water. I have a TDS meter in order to read the PPM and the water prior to putting it the black container is at 4 PPM but over the course of a couple days the PPM rise quite high for some reason. Over 2 days it has gotten to about 40 PPM. I do not have any pots with potting soil sitting in the water and I did not think that perlite would disolve so quick in water.

What is causing this rise in TDS so quick?!

Thanks for your help

[marcel]

I wouldn't look at the perlite, it is inert and shouldn't cause the problem.
two "options":
1. something else in your soil mix (like sand that isn't clean) is possible
2. A bit more off...something is contaminating the water, like the cat peeing in it, bird droppings or even rats or mice. Look for traces of that (smell, flakes, etc)

[frenchy87128]

I cant figure out what the cause would be with everything I can think of. I use peat moss, LFS, vermiculite, and perlite. I have no pets and the container is indoors so there is no organic compounds being introduced that I would be unaware of. I dont fertilize the plants.
I have cleaned the container and the TDS drops after I clean but after a few days it rises again. There is a few pieces of algae in the container that do form but I highly doubt they would be causing the increase in TDS. Maybe dust is the culprit?

So confused!

[marcel]

No, the algae won't cause it but they are an indicator of the presence of nutrients, mainly N and P will cause algae to grow.
Something is creating a lot of plant food and doing it fast.
If it is the peat moss or LFS that is being degraded you should see a kind of "burn" colour, but that would also mean that you have high temperatures and a fluctuating water level to allow oxidation.

[frenchy87128]

The oldest pot I have in there is a little less than 1 year old so I dont think it is being degraded yet. I usually thought it took about 2 years to start doing so. The water level doesnt really fluctuate either as I always have plenty in there to keep them sitting in at least 1/4 inch of water minimum. Could it be the brand of peat moss? I just used a bag of Schultz peat moss but the ingredients on the back state Canadian sphagnum peat so I figured it'd be safe to use but I have read some negative feedbacks on it's quality.
I dont see any burn color on the soil and the temperature never gets higher then 80 and no lower then 70. It's usually always around 75.

[Aidan]

The vermiculite may be the cause. I know of several people who have had bad experiences with it and the general advice is not to use it.

[frenchy87128]

I use it for my Pings, I have heard the same thing as well as with perlite but I didnt think it would happen this quick after only a few days : /

[Aidan]

But it's not a matter of days... it's however long your plants have been potted which you say is approaching a year. I'm not pinning the blame on the vermiculite, I'm saying it's a possibility as it is known to break down over time. Anyway, if the TDS reading does not rise above 40ppm, your plants should not suffer. 50ppm or lower is oft quoted as being the ideal.

Horticultural grade perlite should not cause any problems and a great many growers make use of it.

I use no "fillers" in media other than lime-free grits and sands. Perlite, vermiculite etc are not requirements for any mix and the vaunted claims made of these substances are just that... claims.

[Brian Barnes]

Hi Frenchy,

What sort of peat did you use? There are a few brands offered in garden centers that are quite deadly to CP and may cause the effects you mention. You really have to look at the labels closely anymore, because most brands do say "Pure Canadian sphagnum" on the front and then state "enriched" in the fine print.

Happy Growing,

Brian.

[frenchy87128]

Hi Brian,

That was my first reaction as well so I checked to see if there was anything on the package such as enriched or pre-moistened but the original sphagnum I used was a big bale and I believe the brand was premier. The fine print said pure Canadian sphagnum peat. For the most recent batch I had a small bag of Schultz peat moss and it too on the back says Canadian sphagnum peat. I've just tried separating the 'old' batch from the new batch to see if maybe the soil is already degrading. It might be the case but I'm just hoping I can figure what's causing it!

Thanks,

Yann

[Not a Number]

Premier in bales should be safe to use.

[jj1109]

the problem i had with vermiculite / perlite was every time i had heavy rain (not that often here nowadays!) that flooded the pots, the stuff would float to the top and blow away in the next gust of wind!

[pramudo]

40 ppm is not high and is nothing to worry about. any water (especially deionized water) will dissolve a little bit of anything it comes in contact with. this includes your potting media, but that doesn't mean it will hurt you plants. CPs dislike water with high mineral content but the rise in TDS you detected with your meter is more likely from organic compounds (organic acids) from the peat moss as well as carbonate from reactions with the atmosphere. In other words the water is not gaining any significant concentration of minerals.

Also,your "TDS" meter doesn't really measure total dissolved solids- it measure conductance. the number is then translated using an factory calibration to a salt solution with a known tds. these meters are only accurate within in a narrow range and with a sample of similar composition to the calibration solution. TDS is measured by drying a measured quanity of water and weighing the solids left behind after drying.

deionized water has a lower TDS than just about any water you could find in nature. so you can put the tds meter away , you have plenty of other things to worry about- light, temperature, humidity, pests, etc.