Magnesium is commonly deficient in most systems
Magnesium deficiency is arguably the most common deficiency. Luckily, it is also one of the simplest nutrients to supplement- you can supplement magnesium with Epsom salt. This article will discuss how to supplement magnesium with Epsom salt.
Supplementing with Epsom salt
A naturally occurring mineral, Epsom salt -or magnesium sulfate- has been used for a variety of purposes including digestive health and treating infections. (In fact, Epsom salt can positively impact the health of your fish.)
The white granular salt (edible but not palatable) is easily dissolved in water, and fortunately for us aquaponic and hydroponic growers, it is harmless to fish in the correct dosage. Some people even add Epsom salt to their aquariums purposefully to treat infections. It's usefulness extends into hydroponics and aquaponics as well, as it is a safe and quick way to supplement magnesium.
If you're using hydrated lime with high magnesium content, (i.e. hydrated lime made with dolomitic lime) you probably won't need to supplement magnesium. For most systems, however, especially systems with high nutrient consumption, magnesium is a common deficiency. You can buy magnesium sulfate at any aquaponics store, but unless you are using huge amounts, it will be much cheaper to buy a pound or two at your local dollar store.
Adding Epsom salt
When adding Epsom salt to your system, you'll want to add a dry ounce for every 1000-1500 gallons. This comes to about a tablespoon for a regular sized IBC.
In hydroponics, add the salt to the sump tank.
For an aquaponic system, the salt can be added to the fish tank.
In either system, adjust amounts if deficiencies don't visibly improve. After a while, you will work out a schedule for adding Epsom Salt.
What about magnesium sulfate?
Maybe you saw the name "magnesium sulfate" and thought, "Oh! It must treat sulfur deficiencies as well!" Well, you are correct. (Sort of.) Sulfur is very seldom deficient, but if you are putting magnesium sulfate into your system on a regular basis, you will rule out sulfur deficiencies almost completely. This makes Epsom salt a triple benefit to your system; it's main function is a magnesium supplement, but it also supports fish health and discourages sulfur deficiencies.
Why wouldn't you use Epsom salt?
Download Our Nutrient Deficiencies Key
Magnesium deficiencies are common in plants. Symptoms include interveinal chlorosis with old growth falling off, and occasional burning along the edges of the leaves.
For more clues on how to diagnose nutrient deficiencies, check out [previously free] our Nutrient Deficiency Key.