What Fertilizer to Use in Hydroponics

Your fertilizers are perhaps the most important component of any good hydroponics setup. Lights and good nutrition guarantee great growth, big buds and an abundance of marijuana every eight to nine weeks.

 As you grow more seasoned at the art of cultivating potent marijuana, you will come to know different nutrient solutions, brands, and balances for each strain of plant, and the environment it has grown in.

Here we’ll be taking you through a look at what fertilizer to use in hydroponics to guarantee the success of your grow op. After going through our guide, you’ll know exactly how to get started. 

Source Water

Source Water 

All source water in a hydroponic system needs to be pure. Tap water does have the calcium and magnesium which purified water is lacking by-default, but it also contains a host of organic and inorganic compounds. These pollutants can only be removed through extensive purification making it almost essential for the grower to buy distilled or reverse osmosis water for all nutrient solutions and the reservoir itself. 

Growth Stages & Nutrients 

The two different stages of a cannabis plant’s lifecycle will require different levels of nutrients. Ultimately, the three core nutrients which plant nutrition hinges upon is Nitrogen, Phosphorous and Potassium. Plants in their vegetative state need a high amount of nitrogen, medium to high phosphorous, and a high amount of potassium.

Once flowering, their needs change to a low amount of nitrogen, a high amount of phosphorous and a high amount of potassium. Plants require other nutrients, minerals, and micronutrients as well. These include but are not limited to: 

  • Calcium
  • Magnesium
  • Iron
  • Sulfur
  • Boron
  • Cobalt
  • Copper
  • Molybdenum
  • Zinc 
Growth Stages & Nutrients

Calcium and Magnesium 

Calcium and magnesium are the first two basic minerals which you’ll need to add to your hydroponics. You can either purchase calcium magnesium nitrate with is inorganic or go for organic CalMag which is derived from magnesium carbonate.

When you go for an organic solution you get the added bonus of knowing that the nitrates can’t interfere with the flowering cycle of your plant. All CalMag hydroponic supplements are powered and highly water-soluble. 


Nitrogen is essential for all-round growth and the good health of your plant. Cannabis needs a high amount of nitrogen during its vegetative stage and a low amount of nitrogen while it is flowering. 


As the primary nutrient sustaining and promoting root and flower growth, phosphorus is kept at a medium concentration during the vegetative phase, and high while flowering. 


Potassium is a component involved in root growth and is essential to photosynthesis. You’re going to need to keep your potassium high throughout your plant’s vegetative and flowering stage. 

PH Balance 

Whenever you add any nutrients to your hydroponics, you need to pay careful attention to the alkalinity. The optimal PH for cannabis measures between 5.5 and 6.5. If its rising, slack on your solution, adversely supplementing as needed. If you need to make any major adjustments due to a skyrocketing or plummeting pH, then you’ll need to buy a pH Up or Down solution.

Make sure to dilute it with distilled water which has been heated to the same temperature as the water in your hydroponics before adding it to your reservoir. A fish tank heater works great. 

Selecting a Starter Fertilizer 

Picking your first fertilizer for a fresh hydroponics system can be among the most daunting tasks out there. Many growers opt to buy a pre-packaged selection of fertilizers designed to be used together. Combining a fertilizer to use throughout the grow cycle, and a bottle for each cycle, managing your nutrients becomes nothing more than a matter of balancing your PH and adding appropriately.

Alternatively, you’ll have to pick out one of each type of fertilizer at the least. All good fertilizers will state their balance of Nitrogen, Phosphorous, and Potassium, as well as telling you what stage of growth they’re for. If the fertilizer says its ‘10-4-4’ then this means it has a concentration of 10% Nitrogen, 4%Phosphorous, and 4% Potassium. The measure always reads N-P-K. 

Micronutrient Solutions 

Other nutrients can be added to your hydroponics by purchasing liquid or powdered solutions. The liquid is highly preferred as the solubility of every compound can seldom be guaranteed unless you’re dealing with CalMag. 

Adding Hydroponic Fertilizer to Your System 

Always start with a trusted product with tested results. Notable brands come with a steady stream of followers vouching for their results. Never use nutrients designed to be sued to soil growers. If you are adding a new nutrient or mineral blend to your reservoir then make sure to start at 25% of the solution and work your way up, increasing the concentration every two days until full strength is reached.

Check on a day-to-day basis for discoloration or other ill-health. Any plant which is suffering from nutrient toxicity or a solution which has reached too high or too low of a PH should have its root system flushed for the best chance of survival.

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  1. Rattling superb info on your weblog for us growers. Great!

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