All posts by Scott

Testing for Nickel in Aquaponics

This is part of a series on Aquaponic Water Testing.

Nickel is interesting. Unless you are growing pecans, or multi-generational wheat, Nickel will probably not be needed in your Aquaponic system. In Hydroponics: A Practical Guide for the Soilless Grower By J. Benton Jones, Jr ($72 @Amazon), a level of 0.057ppm Nickel has been proposed.

Sufficient nickel for plants should be present as trace in other supplements, such as Azomite or Maxi-Crop.

You may want to test for Nickel if you have used an Inconel based heating element and have unexplained fish deaths.

Testing for Nickel

I have only found one visual method that even comes close to the .05ppm range we are interested in. If you truly want to measure your Nickel levels, Hanna and Hach have excellent methods.

  1. LaMotte 7802 (.5, 1,2,3,4,5,7.5,10)
    $140 / 20 = $7ea
  2. Hanna Photometer HI96740 (0.000 – 1.000ppm; Resolution 0.001ppm)
    Meter: $196@Amazon
    Reagent: $137@CapitolScientific / 50 = $2.74ea
  3. LaMotte Smart3 + 3663-SC (0.0-8.0, MDL 0.15)
    $143.50 / 50 tests = $2.87ea
    With a Minimum Detection Level of 0.15ppm, nearly 3x our suggested level, this nickel test method isn’t appropriate for Aquaponics.
  4. Hach DR900 + 8150 (0.006-1.000; resolution = 0.006)
    $141@Hach / 100 = $1.41ea
    HachDR900 + Hardness (Calcium) Reagent Set, LR
  5. YSI Nickeltest (0-10; MDL 0.12)
    $73.08 / 50 = $1.46 OR $175.74 / 250 = $0.70
    With a Minimum Detection Level of 0.12, YSI’s Nickeltest will be of limited use, except in diagnosing Nickel poisoning.

Supplementing Nickel

Bad news. The National Organic Program does not recognize Nickel as essential. Therefore, any nickel supplementation is against organic rules. Nickel Nitrate or Nickel Sulfate are easily available.

Know of, or use another method of testing for Nickel in Aquaponics? Let me know in the comments and I’ll update this post.


Testing for Molybdenum in Aquaponics

This is part of a series on Aquaponic Water Testing.

Another heavy metal, Molybdenum is necessary and safe to add to Aquaponic systems. Hoagland suggests 0.02ppm, a level we can safely accommodate since the PNEC_Aquatic for Mo is 12.7ppm.

Molybdenum deficiency will include symptoms of nitrogen deficiency. An upward cupping of leaves, and mottled spots turning into interveinal chlorosis may be present. Cauliflower can exhibit a whiptail appearance. While rarely seen, molybdenum toxicity is easy to visually diagnose – leaves will turn a very brilliant orange.

Testing for Molybdenum

While I am listing one color comparator test, most methods that provide the resolution we require will require a photometer/colorimeter.

  1. Hanna HI96730 Portable Photometer (0.0-40.0; Resolution 0.1)
    $209@Amazon meter + $75 / 100 = $0.75ea
  2. Hach MO-LR (0.25 – 3 mg/L)
    $121 / 100 = $1.21ea
  3. Hach DR900 + 8169 (0.02 – 3.00 mg/L; Res 0.02)
    $57.95@Hach / 100 = $0.58ea
    HachDR900 + Hardness (Calcium) Reagent Set, LR
  4. Hach Colorimeter II Moly (0.02 – 3.00 mg/l)
  5. YSI Molybdate LR (0-15; MDL 0.2)
    $35.67/50 OR $73.95/250
    YSI 9300/9500 Colorimeter + YSI-Photometer-Starter-Pack

Know of, or use another method of testing for Molybdenum in Aquaponics? Let me know via the comments and I’ll update this post.


Testing for Zinc in Aquaponics

This is part of a series on Aquaponic Water Testing.

Zinc is necessary for plant growth, but  only small amount are needed. A deficiency can show itself as interveinal yellowing and pitting on younger leaves, leading to advanced interveinal necrosis. Leaves may also become smaller with shortened internodes.

Hoagland suggests a zinc level of 0.05ppm. That number should be safe in Aquaponic systems, but anything over that would start to cause problems with invertebrates.

Testing for Zinc

Because of the extremely low levels we are measuring, there are no visual methods available to us. Currently, the Hanna HI96731 is a great deal from Amazon if you don’t own a multi parameter colorimeter.

  1. Hanna HI96731 (0.00 – 3.00; Resolution 0.01)
    Meter: $60@Amazon
    Reagents: $48@eSeasonGear / 100 = $0.48ea
    I have this meter. It’s fairly easy to use, but in order to use the meter you’ll need reagents, and a 20ml graduated mixing cylinder.  
  2. LaMotte Smart3+3667-01-SC (0.00-3.00; MDL 0.05)
    Reagents: $112 / 50 = $2.24ea
    Lamotte Smart 3 + Lamotte_Zinc
  3. Hach DR900 + 8009 (.01-3.0; Resolution 0.013)
    Reagents: $58.95@Hach / 100 = $0.59ea
    HachDR900 + Hach8009_Zinc
  4. YSI 9500 + Zinc (0-4.0; MDL 0.02)
    $46.11 / 50 = $0.92ea OR 120.06 / 250 = $0.48ea
    YSI 9300/9500 Colorimeter + YSI-Photometer-Starter-Pack

Zinc Safety

Species NOEC Level, ppm
Bluegill 0.226
Rainbow Trout 0.291
Tilapia 14.0
Hyalella Azteca 0.043
Daphnia 0.021


Adjusting Zinc Levels

National Organic Program states: Zinc carbonate, zinc oxide, zinc silicate, and zinc sulfate may be used to correct a documented zinc deficiency., 205.601(j)(6)(ii) As plant or soil amendments… Micronutrients—not to be used as a defoliant, herbicide, or desiccant. Those made from nitrates or chlorides are not allowed. Soil deficiency must be documented by testing.

I use zinc sulfate. I ordered a 1lb bag from Ebay, and was sent a 5 lb bag instead. At my current rate of usage, that should last me several hundred lifetimes.

Know of another way to test for Zinc in Aquaponics? Or have a different supplement regime? Let me know in the comments and I’ll update the page.


Testing for Silica in Aquaponics

This is part of a series on Aquaponic Water Testing.

Silica can strengthen cell walls,help regulate uptake of toxic elements, increase heat tolerance, and slow transpiration. That leads to more upright plants with increased disease and insect resistance. Silica is not necessary for all plants, but may be beneficial to some species. Research has shown that Tomato plants require between 5 – 20 ppm silica for normal growth (link).

In an aquaponic system, I like to aim for a level of 30ppm SiO2.

Testing for Silica

The first two entries are both “Aquarium level” test kits. Use them with caution. I have and use the Hanna Checker HI770.

If you use Fe-EDDHA or Fe-HBED, you will experience interference.

  1. Seachem Multitest Silicate (0-25)
    $19.08@Amazon / 75 = $0.25ea
    Seachem MultiTest Silicate
  2. Salifert Silicate Profi-test (0-30)
    $21.99 / 60 = $0.37ea
    Salifert Silicate Test
  3. Hanna Checker HI770 (0-200; Resolution 1ppm)
    $51.05@Amazon meter + 6 tests.
    Reagents $34@Amazon / 25 = $1.36ea
  4. LaMotte 4463-01 (5, 10, 20, 30, 40, 60, 80, 100)
    $70.16 / 50 = $1.40ea
  5. LaMotte Smart3 + 3687-SC(0.0-75.0)
    $40.66@GlobalWater / 50 = $0.81ea
    Lamotte Smart 3 +
  6. Hach DR900 + 8185 (1 – 75)
    $72.95@Hach / 100 = $0.73
  7. YSI 9500 + Silica HR (0-150; MDL 0.5)
    $56.55 / 50 = $1.13 OR $139.20 / 250 = $0.56

Know of another way of testing for Silica in Aquaponics? Let me know via the comments and I’ll update this page.


Testing for Copper in Aquaponics

This is part of a series on Aquaponic Water Testing.

Copper is necessary in an aquaponics system in small amount for proper plant growth.

Copper deficiency symptoms include leaves curling and bending downward, a light chlorosis and loss of turgor in young leaves, sunken necrotic spots on leaves, and small leaves.

Hoagland suggests a level of 0.02ppm, which should be safe for aquatic organisms given that the PNEC_Aquatic is 0.03ppm.  Most fish can handle larger amount of copper, but invertebrates such as shrimp, crayfish, and snails are very sensitive. Plant roots may start to experience damage at levels >0.1ppm. At 0.3ppm copper begins to inhibit the bacteria responsible for ammonia and nitrite oxidation.

Testing for copper

Most visual colorimetric tests do not have enough sensitivity, however the Taylor K-1730 is on the borderline, and will allow basic copper determination. The most accurate copper tests use the Porphyrin method (Such as Hach 8143), which does not form a strong visual indicator.

  1. Taylor Technologies K-1730 (0, 0.05, 0.15, 0.3, 0.5, 0.7, 1.0)
  2. Hanna HI3856 (0.00, 0.05, 0.10, 0.15, 0.20, 0.25 ppm)
    NOT AVAILABLE. Manufacturer contacted but even they don’t know why they stopped making it.
  3. Hanna HI96747 (0.000 – 1.500; Resolution 0.001)
    $188 meter @Amazon + $98 @ESeasonGear / 100 = $0.98ea
  4. LaMotte Smart3 + 3640-SC (0.00-3.50; MDL 0.04)
    $27.75 / 100 = $0.28ea
    Lamotte Smart 3Lamotte_3640sc
  5. Hach DR900 + 8506 (0.04 – 5.00)
    $38.75@Hach / 100 = $0.39ea
    HachDR900 + Hach8506
  6. Hach DR900 + 8143 (0.000 – 0.210)
    $190@Hach / 100 = $1.90
    The _most_ accurate method available.
    HachDR900 + Hach8506
  7. YSI Coppercol (0-5.0; MDL 0.03)
    $48.72 / 50 = $0.97ea OR $126.15 / 250 = $0.50ea

What if my copper is too high?

If your copper level is above where you want it and you have sensitive organisms such as shrimp or crawdads, you have two options: Water changes, or CupriSorb. CupriSorb is expensive, but may be regenerated once it’s full of copper.

If your copper level is too high, it’s important to investigate why. If your source water is high in copper you could use a R/O machine or treat makeup water with a bag of CupriSorb.

What if my copper is too low?

Copper Sulfate or Copper Nitrate are the most commonly used forms of copper. Be very careful as you’ll be measuring tenths of grams if you decide to supplement.

Know of a different way to test for Copper in Aquaponics? Let me know in the comment section and I’ll update this post.

Testing for Potassium in Aquaponics

This is part of a series on Aquaponic Water Testing.

Potassium is very important to plant growth. A Potassium deficiency will cause older leaves to appear chlorotic, and uneven ripening(if at all) in fruit. Unfortunately, fish require no dietary Potassium. Therefore most fish feed is not supplemented with Potassium.

How much Potassium?

Hoagland suggests a plant “ideal” of 235ppm. Another approach is to aim for a value 2/3 of your nitrate levels, or twice your phosphate levels. Excess Potassium may lead to deficiencies in Magnesium, Manganese, Zinc, and/or Iron.

 Potassium Testing Methods

There are two methods of testing for Potassium; turbidity based tests, or using an Ion Specific Probe. I have the LaMotte Double Tube test kit, and it works, but is cumbersome. I have also used the YSI method and love the ease and rapidity of the test. It does have a low range (0-12ppm), I usually diluted my sample 10 to 1 which increases that range to 0-120ppm.

  1. LaMotte 3138-01 Double Tube (0, 6, 7, 10, 20, 30, 40, 50)
    $65.20 / 100 = $0.65ea
    I have and use this double tube setup. If my potassium is >50, I could re-run the test after diluting the sample with distilled water, but often don’t.
    Lamotte 3138-01
  2. Hanna HI96750 Portable Photometer (10-100; Resolution 1)
    Meter: $176 / $196@Amazon
    Reagent: $85 / 100 = $0.85ea
  3. LaMotte Smart3 + 3639-SC (0-10.0, MDL 0.8)
    $59.65 / 100 = $0.60ea
  4. YSI YPM189 (0-12; MDL 0.5)
    $35.67 / 50 = $0.71ea OR $79.17 / 250 = $0.32ea
  5. Horiba LAQUAtwin Potassium 39-3900ppm
    Meter: $320@Amazon +
    Sensor: $127@Amazon / 1500 = $0.08ea
    Requires calibration before every use.

Potassium Supplementation

There are a number of chemicals we can use to supplement the Potassium in our Aquaponics systems. I use MonoPotassium Phosphate, Potassium Nitrate, Potassium Bicarbonate, and Potassium Silicate. I save my banana peels for my compost bins.

  1. Potassium BiCarbonate
  2. Potassium Hydroxide
  3. Potassium Nitrate
    I love potassium nitrate. For every 3ppm Potassium added, you also get 1ppm Nitrate.
  4. Potassium Sulfate
    Potassium Sulfate works, but since plants don’t use as much sulfate as potassium, you could end up with sulfate issues.
  5. Mono Potassium Phosphate (MKP)
  6. Potassium Silicate
    Allowed in organic production as Sil-Matrix, an aqueous Potassium Silicate, as a “pesticide”.
  7. Banana Peels
    Not recommended. The number of banana peels needed means your growing media would be banana peels, not rocks.

Do you know of a different way of testing for Potassium in Aquaponics? Let me know in the comments and I’ll update this page.


Testing for Boron in Aquaponics

This is part of a series on Aquaponic Water Testing.

Boron deficiency can be seen as interveinal chlorosis of upper leaves, brittle leaves, and stunted growth. On celery, Boron deficiency is easily noticed as “cat-scratch” marks on the plant stems.

Boron levels in Aquaponics

Hoagland suggests a Boron level of 0.5ppm. Levels above 1ppm can be toxic to plants. Because of this, I greatly recommend testing your Boron levels before you supplement. Supplementing Boron without testing is a recipe for disaster!

Testing for Boron in Aquaponics

Unless you have a LaMotte Smart3 Photometer, the Hanna HI38074 is your only bet for measuring boron levels yourself.

  1. Hanna HI38074 (Resolution = 0.2ppm)
    $65/100 = $0.65ea
    I use this test kit, and if you can follow directions, you should be able to complete this titration. Includes a digital pH meter!
    In this titration, one drop < 0.2ppm. That means if your result is 3 drops, your Boron reading is less than 0.6ppm.
  2. Taylor Technologies K-1541 (Resolution = 0.2ppm)
  3. Salifert Boron Test (Resolution = 0.5ppm)
    $29.46/25 = $1.18ea
    For reef aquaria only, expects pH 8-8.6. Don’t use for Aquaponics!
  4. LaMotte Smart3 + 4868 (0. 0-0.80, MDL .05)
    $102@GlobalWater /50 = $2.04ea
    Lamotte Smart 3 +
  5. Hach DR900 + 10252 (2 – 50; Resolution = 2.2ppm)
    $289.95@Hach / 100 = $2.90ea
    Gaseous Hydrochloric Acid forms when mixing reagent. Use Caution! Also, this method only has sufficient resolution when used with a spectrophotometer, such as the DR1900.
    HachDR900+Hach10252_Boron HR
  6. Hach DR1900 + 8015 (0.2 – 14.0)
    $289.95 / 100 = $2.90ea
    Gaseous Hydrochloric Acid forms when mixing reagent. Use Caution!
    Hach_DR1900Hach10252_Boron HR
  7. YSI 9500: Method discontinued

Know of another way of testing for Boron in Aquaponics? Let me know in the comments and I’ll update this post.


Testing for Manganese in Aquaponics

Manganese is an essential micronutrient for plants, participating in several metabolic processes – mainly photosynthesis. Of course, an excess amount is toxic.

Deficiency symptoms can include: Interveinal chlorosis on older leaves, light green leaves with dead patches ringed in yellow, few flowers or fruit. Interveinal Chlorosis and few flowers/fruit can have many causes, so testing is recommended to determine actual deficiency.

Hoagland suggests a Manganese level of 0.5ppm. While higher than the PNEC_Aquatic of 0.246, a review of common Aquaponics organisms suggests that levels <1ppm should be safe.

Unless you have a colorimeter, your best bet is the SenSafe Manganese test strips. These aren’t normal test strips, but the directions are clear.

  1. Hanna HI38042 (0-3.0mg/l, .2mg/L) DISCONTINUED
  2. LaMotte 3588-02 (0.05,0.1,0.2, 0.4, 0.6, 0.8, 1.0)
  3. Hach MN-PAN (0.05 – 0.7; Resolution = 0.05)
    $179/50 = $3.58ea
  4. Hanna HI96709 Portable Photometer (0.0-20.0; Resolution .1)
    $183@TestEquipmentDept meter + $35.49/100 = $0.35ea
  5. LaMotte Smart3+3658-01-SC (0.0-0.7, MDL .01)
  6. Hach Colorimeter II Manganese LR (0.01 – 0.70; Resolution 0.01)
    $430meter + 50 tests. Uses 8149 Method.
    Hach_PCII_Manganese_LR + Hach8506
  7. Hach DR900 + 8149 (0.006 – 0.700; Resolution = .006)
    $51.95@Hach / 100 = $0.52ea
  8. SenSafe Manganese Test Strips (<0.02, 0.05, 0.1, 0.2, 0.5, 1.0, 2.0 ppm)
    $26.99@Amazon / 24 = $1.25ea

Know of a different or better way to test for Manganese in Aquaponics? Let me know in the comments and I’ll update this post.

Testing for Iron in Aquaponics

This is part of a series on Aquaponic Water Testing.

Iron is one of the most common deficiencies in Aquaponics systems. The main symptom of a deficiency is interveinal chlorosis on the newest leaves of the plant. Many other deficiencies cause interveinal chlorosis, so relying on visual identification can be hard, especially for inexperienced growers.

Aquarium test kits, like the Seachem MultiTest Iron, should be avoided if possible. They lack the ability to accurately check for chelated iron. However, they will answer the question “Is there Iron?”

I own and use the Hanna Checker HI721.

If you use Fe-EDDHA, or Fe-HBED in your system, beware test interference. The YSI MR test is the most accurate test I’ve found. It separates out the Iron Reducer and the phenanthroline reagent, allowing for the photometer to be zeroed in between the two steps.

  1. Seachem MultiTest Iron
    $13.09 / 75 = $0.17ea
    Seachem MultiTest Iron
  2. Hanna Checker HI721 (0.00 – 5.00; MDL 0.01; Resolution 0.01)
$49.13@Amazon Meter + 6 tests.
    $6/25 refills=$0.24 ea
    HI 721 Iron Meter
  3. LaMotte Smart3 + 4315-H (0.0-10.0, MDL 0.05)
    $37 / 100 = $0.37ea
  4. Hach DR900 + 8008 (0.02 – 3.0; Resolution = 0.021)
    $21.95@Hach / 100 = $0.22ea
    HachDR900 + Hach8506
  5. YSI 9500 + Iron MR (0 – 5.0; MDL 0.02)
    $46 / 50 = $0.92ea OR $104.40 / 250 = $0.42ea
  6. YSI 9500 + Iron HR (0-10.0; MDL 0.05)
    $23.49 / 50 = $0.47ea OR $46.98 / 250 = $0.19ea

Have I missed an Iron test that would work for Aquaponics? Let me know in the comments and I’ll update this page.

Testing for Magnesium in Aquaponics

This article on Magnesium Testing is part of a series on Aquaponic Water Testing.

Magnesium is important for photosynthesis in plants. It forms the center of the chlorophyll molecule. If deficient, plants will begin breaking down chlorophyll in older leaves, leading to the symptom of Interveinal Chlorosis in those older leaves.

Beware, Zinc deficiency produces the same symptoms. Ensure your magnesium levels are correct before considering Zinc. If you have interveinal chlorosis in older leaves and your Mg2+ levels are fine, take the time to test for zinc.

Hoagland suggests a Magnesium level of 48 ppm. The ratio of Magnesium to Calcium is important as well.

Measuring Magnesium

Your magnesium level can be measured, or calculated. Calculation is the traditional method. The Red Sea kit is an example of a direct titration, while the YSI Magnicol is a colorimetric test.

  1. Red Sea Magnesium Pro (Resolution 20ppm)
    $30.36 / 100 = $0.30ea (@Amazon)
    Red Sea Magnesium Pro Test Kit
  2. YSI Magnesium Magnicol (0-100; MDL 2; ±1)
    $38.40 / 50 = $0.77 OR $62.64 / 250 = $0.25

Calculating Magnesium.

Total Hardness = Calcium Hardness + Magnesium Hardness + divalent metal hardness.

We can safely ignore (and some tests specifically mask out) metal hardness in our tests.  That means if we test for Total Hardness and Calcium (or Calcium Hardness), we can calculate Magnesium Hardness. When calculating, your results will only be as accurate as your source measurements. Use a higher resolution method for the Calcium test, such as with the Hach Digital Titrator, or pool chemicals in order to get accurate results here.

Most calcium tests give the results in the form of Ca2+. In order to convert that to Calcium Hardness, we multiple it by 2.5.

Total Hardness = (Ca2+* 2.5) + Magnesium Hardness

Magnesium Hardness = Total Hardness – (Ca2+* 2.5)

Once we do our subtraction, we can convert Magnesium Hardness to Mg2+ by dividing by 4.1

Mg2+ = Magnesium Hardness / 4.1

Know of a different way to test for Magnesium in an Aquaponic system? Let me know in the comments and I’ll update the post.