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.
- Hanna HI38042 (0-3.0mg/l, .2mg/L) DISCONTINUED
- LaMotte 3588-02 (0.05,0.1,0.2, 0.4, 0.6, 0.8, 1.0)
- Hach MN-PAN (0.05 – 0.7; Resolution = 0.05)
$179/50 = $3.58ea
- Hanna HI96709 Portable Photometer (0.0-20.0; Resolution .1)
$183@TestEquipmentDept meter + $35.49/100 = $0.35ea
- LaMotte Smart3+3658-01-SC (0.0-0.7, MDL .01)
- Hach Colorimeter II Manganese LR (0.01 – 0.70; Resolution 0.01)
$430meter + 50 tests. Uses 8149 Method.
- Hach DR900 + 8149 (0.006 – 0.700; Resolution = .006)
$51.95@Hach / 100 = $0.52ea
- 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.