quailrancher
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Joined: Sat Jul 26, 2014 4:42 pm
Location: San Jacinto, CA Zone 8b Sunset Zone 19

Precipitation Problem

I set up a deep water system (with bubblers) for a friend. Nine tubs with a total capacity of 150 gallons. I used MaxiGro 10-5-14 to get started while waiting for my order of a two part nutrient package from American Hydroponics to arrive.
The MaxGro resulted in a ppm of slightly over 900 in all tubs. This is with water that has a ppm of 231 to 278 and a ph of 7.2. The pH of the solution ranged from 5.87 to 6.12. Solution temperature reaches 80 degrees F (it's hotter than hell here), and this is an outdoor installation under shade cloth. The crop is strawberries, so the pH is correct.

But now, four days later, the solution ppm has dropped to 108 to 130 in five tubs. I can see the precipitate on the bottom of the tubs. The pH remains unchanged.

Strangely, the ppm in the remaining four tubs remains at around 900. Same water, same amount of nutrients. No sign of precipitate. I'm having trouble wrapping my head around this.

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JC's Garden
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Joined: Tue May 13, 2014 2:43 am
Location: Moultrie, GA Planting Zone 8, Sunset Zone 31

Re: Precipitation Problem

I'm commenting just to follow your post and see how this turns out. Good luck.
It will help others if you give your location. :)

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Lindsaylew82
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Location: Upstate, SC

Re: Precipitation Problem

I'm not up on hydroponics, but I used to be an avid aquarist and I have a very large understanding of water chemistry, precipitates, etc...I grew heavily planted amazon black water tanks. (Now that my home renovations are NEARLY done....I may have time again for a second hobby :() )

In my NEW tanks, I always had issues with keeping plant nutrients up (in the form of nitrAtes) with initial algae bloom. Especially if I used old rocks or sand. Algae are high eaters. In my very mature systems, my nitrogen cycle is on point and efficient. I have enough fish to produce an end result nitrAte for the plants in the tank, but an algae bloom can totally ruin a system. 1 little thing is all it takes.

Were the tubs that are eating through the nutrients from a previously mature system? Are they re-used?

Just a shot in the dark....
Lindsay
Upstate, SC
USDA Zone 7b/ Sunset Zone 31

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Lindsaylew82
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Location: Upstate, SC

Re: Precipitation Problem

Something about dissolved o2 binding with something or another blah, blah....can cause precipitate. Hard water...blah blah...soft water....

There are a lot of missing pieces. I need to brush up.

I'm interested now :-()
Lindsay
Upstate, SC
USDA Zone 7b/ Sunset Zone 31

quailrancher
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Joined: Sat Jul 26, 2014 4:42 pm
Location: San Jacinto, CA Zone 8b Sunset Zone 19

Re: Precipitation Problem

Lindsaylew82...

I don't think the nutrients were being taken up by anything. I think the total dissolved solids in the household water was causing the nutrients to precipitate out. Then to go back into solution (in some tanks) and back out again. That's the puzzling part. I'm now thinking in terms of a reverse osmosis system to get the TDS in the water supply down to a few ppm. Prices have come down on RO filters, so I should be able to put filter, pump and plywood tank together for about $250. I sure will be glad when this project is finished.

quailrancher
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Posts: 4
Joined: Sat Jul 26, 2014 4:42 pm
Location: San Jacinto, CA Zone 8b Sunset Zone 19

Re: Precipitation Problem

A post got lost somewhere. I'm in Zone 8b, where the temperatures are typically around a hundred for three months. I have a mister under each raised tank. This seems to keep solution temperatures at 80 degrees, as opposed to 84 or 85 without. It would work better if the humidity was the usual 25-30%, but this is a bad year.

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Lindsaylew82
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Location: Upstate, SC

Re: Precipitation Problem

I would think that hardness of water would effect the dissipation of nutrients via chemical bonding that caused the precipitates. But the ph would be fluctuating... I know you said that the ph was constant, but maybe you should check the ph at different times during the day. Temperature can make ph go up or down, and high ph can make certain mineral dissipate in the water column via precipitation. Also very HARD water will lend to a more unstable ph in new AQUARIUMS, but I don't know about large grow tanks...

Another shot in the dark... Maybe this'll trigger some lightbulbs?
Lindsay
Upstate, SC
USDA Zone 7b/ Sunset Zone 31

quailrancher
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Posts: 4
Joined: Sat Jul 26, 2014 4:42 pm
Location: San Jacinto, CA Zone 8b Sunset Zone 19

Re: Precipitation Problem

Lindsaylew82...

I know that you should never mix two-part nutrients when in concentrated form, but--in the case of the American Hydroponics two part nutrients--the finished dilution would be 1400 ppm, which is more concentrated than the solution I have. Of course there's no problem with that dilution. I did read that a small amount of precipitation is normal, given the manufacturing process (some salts are meant to precipitate out). That doesn't affect the desired ppm.

I see that temperature can have an effect. Calcium sulfate will precipitate out, but at a temperature that would cook the strawberries. With my setup, we're talking about eight degrees R from coolest to warmest. The most baffling thing is how the ppm can go from 900 to about 100, then back up to 800 or so. A couple of tanks are unaffected. I check various parameters twice a day (pH, ppm, and solution temperature). I have two ppm meters, so I've eliminated device error.

I'm going over to check things again. when the solution is at its coolest.

I may have to post in a hydro pot growing forum. Some of those guys are chemists (the ultimate cash crop, so expertise pays off).

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DDMcKenna
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Location: Florida, USA, just north of Daytona Beach

Re: Precipitation Problem

This could be interesting ;)

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Lindsaylew82
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Joined: Thu May 22, 2014 1:26 am
Location: Upstate, SC

Re: Precipitation Problem

I may have to post in a hydro pot growing forum. Some of those guys are chemists (the ultimate cash crop, so expertise pays off).
HA! Funny you should mention, I was looking up something on thrips, and I kept getting rerouted to pot forums... It was still helpful! :roll:
Lindsay
Upstate, SC
USDA Zone 7b/ Sunset Zone 31

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