I use General Hydroponics three part nutrient system: Micro (5 0 1) Gro (2 1 6) and Bloom (0 5 4). It is reliable and gives me more options to refine the mix. I filter my water using a reverse osmosis system so I start out with pure water, no sediments or chemicals. I add Cal-Mag to my mix because cannabis plants need extra calcium and magnesium which have been removed by the RO filter. To regulate the pH I use Up and Down from General Hydroponics.
I buy one gallon containers because they are much cheaper than quarts. I fill hydrogen peroxide containers to reduce spillage when measuring amounts to add to the solution. Each part of the solution must be added in a certain order and thoroughly mixed before adding the next part to the reverse osmosis filtered water.
With the intense light and optimum environment these plants will develop quickly. You can get a good idea of the amount of nutrients to use by comparing the color of the original solution with the solution that is left in the bucket. The solution should be lighter colored but not too light. (See images.)
If the solution at the end of the week is very light colored I know to add more nutrients the next week. I believe this indicates the plant has removed almost all of the added nutrients.
Conversely, if there is little or no change you should add less and look for signs of nutrient toxification, leaf tips turning down or brown tips. To make things more complicated the solution for a light feeder may look the same at the end of the week. You need to make sure the plant has healthy green leaves and is producing new stems.
It takes some experience to judge the right amount of nutrients for each strain. The change in color is relative to the amount of nutrients you originally use for the solution. Some plants will use a lot of solution during the week, most average 2 liters a day, so you need to use the same amount when adding more.
Since adding better air stones and splitting the 6 buckets between two 1000 gph air pumps some plants need more nutrients and some need less. I am dividing different strains into 3 categories. Average feeders which are plants that do well at the recommended amount suggested by the manufacturer of 5 milliliters of each nutrient to 4 liters reverse osmosis filtered water. This amounts to 20 ml in the 16 liters I use in each bucket. Heavy feeders get 25 ml of each nutrient and light feeders get 15 ml of each.
I used to reduce nutrients (except for bloom) when I started the plants to flower. With the increased air flow some of the plants leaves begin turning yellow, a sign of nutrient deficiency. The plant quickly recovered once I resumed using 25 ml / bucket. On the other hand at the same time another strain got nitrogen toxification from too high a level of nutrients while beginning the flower stage. I have been keeping the level of nutrients (except bloom) the same as during the vegetation stage.
I do not flush my plants in the last week of flowering. A very well done study from The Atrium has shown that flushing has no affect on the chemical composition of the plant. For an interesting look into this research go here. High Times has its own take on the practice.
I use equal parts of the three General Hydroponics system (Micro, Gro and Bloom) and a Calcium and Magnesium supplement except during the flowering stage when I will increase the amount of Bloom.
Clones
10 ml / 10 liters
Vegetation Stage
Weeks 1 – 6
Normal – 20 ml / 16 liters
Heavy – 25 ml / 16 liters
Light – 15 ml / 16 liters
Flower Stage
Week 1
Normal – 20 ml + 40 ml Bloom
Heavy – 25 ml + 40 ml Bloom
Light – 15 ml + 30 ml Bloom
Week 2
Normal – 20 ml + 50 ml Bloom
Heavy – 25 ml + 60 ml Bloom
Light – 15 ml + 40 ml Bloom
Until harvest
Normal – 20 ml + 60 ml Bloom
Heavy – 25 ml + 70 ml Bloom
Light – 15 ml + 45 ml Bloom
Growing medical cannabis 