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I'm small scale market looking to grow. I will also be working on another hydroponic startup.

I bought an Oakton waterproof ph meter and a hanna checker for iron the other day.

I read a pdf talking about fish stocking vs plants from Aquaponic Solutions. I'm not sure the policy on posting links, so if you google that they come up, and it's under the link fact sheets.

Anyway, it talks about the UVI method of feeding excess food in order to bring up the micronutrients to needed levels. This had me wondering if plants in understocked / underfed systems have micronutrient deficiencies that may not show through the plants but slow growth or reduce flavor. I'd like to have his formulas to look through, oh well.

Since I had the Hanna Iron Checker, I decided to take a look at the other Hanna checkers. Then found the multi testers and had some questions.

I see there are tests for phosphorus and phosphate, what is the difference and which one for aquaponics?

There are silica tests, what does one add to the system for silica? I am growing out tomatoes and cucumbers.

What is the best multi meter? The ysi 9500 or the  LaMatte SMART 3? Looks like there's some things one checks the other doesn't that would be useful.  Or is there a better one?

I'm wondering if the other micro nutrients are worth tracking or just use the checkers though they don't measure potassium.


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Looks like the YSI 9500 only measures phosphates and not phosphorus, and the LaMatte requires a heater block to measure phosphorus.

Hi Devoid...To convert your phosphate measurement (ppm or mg/L) to phosphorous just divide your measured phosphate value by 3.0645

Potassium would be a VERY useful thing to track/measure.

For silica, I add potassium silicate. The silica helps with cell wall turgidity/strength. It's really quite useful for plants like cucumbers whose leaves have cells with relatively weak cell walls. It's this weak cell wall structure that make them so susceptible to things like Powdery Mildew...


What do you use to measure potassium and what levels do you run?

The big meters are costly but I'm wondering about adding up the costs of all the useful single test meters. Which parameters would you suggest measuring for market gardener looking to scale up? What if one looks to do hydroponics as well or instead?

My whole system is raft culture, based on friendly aquaponics. I know Tim preaches low density, after reading the pdf though I wonder if it has micro nutrient deficiencies though. I'm looking to build a new fish tank for my current system and wanting to properly size it to be able to grow out full of tomatoes, cucumbers, and peppers. I have 752 sq ft of raft. Unsure my total fish weight at this point and not even sure how to estimate it at this point.

Crap lost my post in progress.

Is it worth getting a checker for ammonium, nitrates or nitrites, or are the strips good enough?

I'm looking at the silica and phosphorus checkers at $50 each, the hanna potassium meter is $200. Then there is a calcium and magnesium photometer for $200 (HI 96752). I'm nearly half way to one of the big meters in just those 3.

Edit: Sorry for all the questions, I'm researching the best I can. Was diagnosed with seizures couple weeks back and the meds have been giving me near migraine level headaches daily.

YSI 9300 is ~$1,000

Has these tests:

The Smart 3 is ~$800

Has these tests, look under Reagent System:

Appears the Smart3 lacks magnesium but the YSI has it. I'll have to do a better comparison after the headache resides.

I have a comparison of aquaponic appropriate water test kits on my blog:

So that's you. I've got a couple comments pending on copper and manganese I believe. Your website is where I was looking at all the meters. I'm a bit too lazy for running titration tests, plus I hate having to decide where the color is on a color chart, I hate guessing


Haha - so those comments are from you. I'm working on my replies... Hanna isn't very transparent about when they stop manufacturing tests.

Titration tests are a pain, but it's the only way you're going to get a boron reading without breaking the bank.

When I absolutely have to use one then I guess I don't have much choice.

It wasn't a big deal about the discontinued meter, was just letting you know so you could update. As I kept referencing your site I thought I'd help just a little.

After reading about testing for all these little nutrients it almost seems like hydroponics is easier.

What about testing for sulphur? I see the big meters have sulfide, sulfate, or sulfite.

Looks like the YSI meter does boron. Another point for multi parameter meter

Yes, the YSI meter has the capability of doing a boron test.  The reagents are no longer sold though. ;-{

oh, that seems weird. drats. Would you go YSI or LaMatte?

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