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.
- LaMotte 7802 (.5, 1,2,3,4,5,7.5,10)
$140 / 20 = $7ea
- Hanna Photometer HI96740 (0.000 – 1.000ppm; Resolution 0.001ppm)
Meter: $196@Amazon
Reagent: $137@CapitolScientific / 50 = $2.74ea
- 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. - Hach DR900 + 8150 (0.006-1.000; resolution = 0.006)
$141@Hach / 100 = $1.41ea
+ 
- 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.