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Feed · Mix nutrients

Dissolve Athena Pro Line powder into a 50 L stock tank

Dissolve a full 11.34 kg (25 lb) bag of Athena Pro Line in a 50 L tank to make a stock concentrate. Add a small quantity of the stock to the feed water to make the feed. This paper shows that the water temperature and the mixing are important at 227 g/L. It shows that Part A and Part B must be in different tanks. It also shows how to calculate the dose in milliliters for each liter of feed.

Feed5 diagrams8 sources~11 min to read
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Purpose and scope

In this paper, the task is to dissolve a full 11.34 kg (25 lb) bag of Athena Pro Line in a 50 L tank. The result is a strong stock solution. Do not give this solution to the plants directly, because it is much too strong. Make the stock solution one time. Then measure a small quantity of the stock solution. Add it to your irrigation tank to make the feed.

A stock tank changes a powder that is not easy to use into a liquid that is easy to use. When you weigh the powder each time you make feed, the procedure is slow and the quantity is not the same each time. Dissolve the full bag one time. Then add the stock to your feed water in a quantity that you measure, in milliliters for each liter. Each time, you get the same feed in seconds.

Terms

Definitions

Stock solution (concentrate)A strong nutrient solution that you keep in a tank and add to the feed water in small quantities. In this paper, it is one full bag in 50 L. Do not give it to the plants directly.
Working solution (feed)The diluted solution that the plants use. You make it when you add a small quantity of stock to a large quantity of water.
Part A / Pro CoreThe part of Athena Pro Line that contains calcium and nitrogen. Put only Part A in its stock tank.
Part B / Pro Grow or Pro BloomThe part of Athena Pro Line that contains sulfates and phosphates. It must have a different stock tank from Part A.
Dose rateThe quantity of stock that you add to each liter of feed water, in milliliters for each liter (mL/L). You use this value each day.
Solubility / saturationThe quantity of salt that a specified volume of water can hold. Water holds more salt when the temperature is higher. If you add more salt than this limit, the salt does not dissolve and stays as grit[3]. Grit is solid particles of salt in the tank.
Precipitation / lockoutDissolved salts make a solid and fall out of the solution. For example, calcium makes a solid with sulfate or with phosphate. The nutrient is not in the water, and the plant cannot use it[2].
EC (electrical conductivity)A meter reading of the total quantity of dissolved salt. You use this reading to do a check of the strength of the feed that you make.
Quality of the information

Evidence and limitations

Three types of information

We want each paper to be correct. Thus we examine each paper for information that is not solid. This information comes from the view of one grower, from a small number of sources, or from grower methods that have no controlled test. We identify this information, and we do not show it as solid.

Frequently there is no paper for the decision that you must make. Then we use the reports of other growers and the methods that work in the rooms that we know. This information can help you, but it is not the result of a laboratory test. Use the methods that work for your plants, for your room and for your meters. If a table does not agree with your crop, use the data from your crop and record the difference.

Solid
Tests of plants, specifications or many sources that agree show that the information is correct
  • When you keep part A and part B apart, calcium does not make a precipitate with sulfate or phosphate.
  • The method to calculate the concentration of the stock solution, for procedures with a specified bag of fertilizer in a specified volume of water.
Grower method
Many growers use this method in their rooms. Start with it, then change it for your room.
  • The Athena Pro Line procedure with stock solutions and doses, as one commercial system of many.
Weak
The view of one grower, a small number of sources, one test, or a method that works in one room
  • A table of doses from a different manufacturer, with no check of the table with your meter and your water.

If you find an error, make a report. We will correct it. Make the report on GitHub, with the name of the paper and the information that is incorrect. If you have a source, include it: Make a report of an accuracy problem. The regulations, labels and licenses of your area always override each procedure in these papers. The label weak in a paper shows the points where the risk of an error is highest.

The primary instruction

Keep part A and part B in different tanks

Put Part A in one stock tank and Part B in a different stock tank. Do not let the two concentrates touch each other. This instruction prevents damage to your crop and to your pump. Put one 11.34 kg (25 lb) bag of Pro Core in one 50 L tank. Put one 11.34 kg (25 lb) bag of Pro Grow/Bloom in a different 50 L tank.

The cause is chemical. Part A contains a large quantity of calcium, and Part B contains sulfates and phosphates. In a diluted feed, there is no problem. But if you put the two concentrates together, the calcium immediately makes a solid with the sulfate and the phosphate. The solid is gypsum and calcium phosphate[1]. The result is a tank of sludge that you cannot use, and the crop does not get the nutrients that you added[2].

Where the two parts touch1Bag A to Tank APro Core stockonly→2Bag B to Tank BGrow/Bloom stockonly→3Feed wateradd A and mix→4Same waterthen add B andmix→5Plantssafe, dilutedfeedThey touch only when diluted in the feed water. Add them one at a time.
Figure 1. If you put concentrates A and B together, they make a precipitate immediately. If you add A and B to the feed water one at a time, the water dilutes each concentrate and they stay in solution. This difference is the cause of the primary instruction.
The cause

How to dissolve 227 g/L fully

227 grams of salt for each liter is a large quantity. It is approximately six to seven times more salt than in seawater. It is not automatic that all the salt dissolves. Two effects can cause some of the salt to stay solid:

  • Salt that dissolves makes the water colder. Most of these salts absorb heat when they dissolve (endothermic). Thus the tank becomes colder when you add powder, and less salt dissolves in colder water[3]. Hot water and a paddle prevent this problem.
  • Cold water and water that does not move become saturated. If you do not use heat and strong mixing, the solution is at the saturation limit. The last part of the bag stays as grit on the bottom. Then the stock has a concentration that is too low, and the concentration is not the same each time.
Hot water dissolves more saltUse hot water because solubility increases with temperature. Salt makes the tank colder when it dissolves.027538010610C20C30C40C50Csolubility index
Figure 2. Solubility increases when the temperature increases. Thus hot water holds more salt. Salt that dissolves makes the water colder, and hot water decreases this effect[3].
The method

Stock-tank mixing procedure

Do the procedure below one time for each part. Do it one time for the Pro Core bag (Tank A) and one time for the Pro Grow/Bloom bag (Tank B). The steps are the same each time.

  1. Start with hot water: approximately 40 L

    Fill the 50 L tank to approximately 40 L with hot water at approximately 40–50 °C (104–122 °F). Keep headroom in the tank. The 11 kg of powder increases the volume. The water must not spill when you mix.

  2. Start the paddle before you add the powder

    Make a vortex in the water with the paddle. The salt must go into water that moves. The salt must not collect on the bottom of the tank.

  3. Add the powder slowly

    Add the powder slowly and continuously. Do not add the full bag at one time. If you add all the powder at one time, clumps occur. A clump holds dry powder in the middle, and this powder does not dissolve (a ‘fish-eye’).

  4. Mix until the solution is transparent

    Continue to mix until there is no grit and the solution is transparent. The solution can have a color. At this concentration, it is possible that you must mix for some minutes, and not for seconds.

  5. Fill to the 50 L mark

    When all the salt dissolves, add warm water until the solution is at the 50 L mark. The concentration is accurate because you add the water after the salt dissolves.

  6. Put a label and the date on the tank

    Write ‘PART A, Pro Core’ or ‘PART B, Grow/Bloom’ and the date on the label. The two tanks look the same. If you use the incorrect tank, you do not obey the primary instruction.

  7. Let the solution become colder, then do a check again

    When the solution becomes colder, look for solid material that falls out of the solution. A small quantity of sediment can show that the solution was near saturation. Mix the solution again. If the sediment stays, it is possible that you must add a small quantity of water.

The sequence for each bag1Hot water ≈40 Lfill first→2Paddle onmake a vortex→3Add bag slowlycontinuous→4Mix fullyno grit→5Fill to 50 Lcorrect strength→6Label: A or Band dateThe same for the two bags. Use two different tanks, each with a label.
Figure 3. The diagram shows all the steps of the method. Do the method two times, one time for each bag, in two different tanks.
The numbers

Stock concentration and dose

A full bag weighs 11.34 kg (25 lb). In 50 L, the stock has this concentration:

Stock concentration from a full bag in 50 L11.34 kg / 50 L = 226.8 g/L. This is the strength of your concentrate.065130195260227 gFor each liter23 gFor 100 mL
Figure 4. 11.34 kg in 50 L = 226.8 g/L. When you know this number, you can change the feed rate on your bag to a dose in milliliters for each liter.

To use the stock, you dilute it. The bag (or the Athena chart) gives the feed rate for a part. The feed rate is X grams for each liter of diluted feed. Use the formula below, because your stock is 226.8 g/L.

Doses for your stock of 226.8 g/L. Each time, make sure that the target rate agrees with your bag, because formulas change.
Feed rate on the labelDose of stock for each liter of feed
0.5 g/L2.2 mL/L
1.0 g/L4.4 mL/L
1.5 g/L6.6 mL/L
2.0 g/L8.8 mL/L
The feed

Feed strength targets for each stage

The stock only supplies the nutrients. The strength of the feed is important for the plant, and you read the strength as EC. A weak feed is correct for plants in the first stage, and a strong feed is correct for plants in the bulk stage. At the end of the cycle, you decrease the strength. The quantity of nutrients that cannabis uses changes during the cycle[4].

Approximate feed EC for each stageApproximate ranges: use your meter and follow the Athena chart for your cultivar.clones / seedlingvegetative stageflower bulkend / decrease0.8 EC2.4 EC4 EC
Figure 5. Use a weak feed in the first stage. Increase the strength in the vegetative stage and the flowering stage. Decrease the strength in the last stage[5]. These ranges are start values. They are not limits. The substrate and the cultivar change the ranges.
When there is a problem

Storage and troubleshooting

SymptomPossible causeCorrection
Grit on the bottom of the tankThe solution is at saturation. The water is too cold, or you did not mix the solution sufficiently.Mix again with the paddle. Increase the temperature of the solution. If the grit stays, add a small quantity of water.
Crystals in the stock after storageThe stock became colder, and salt fell out of the solution. The stock was near saturation.Increase the temperature of the stock slowly and mix it again before you add it to the feed. Keep the stock where it is not cold.
The stock is white and not transparentPossible contamination of the Part B tank with Part ADo not give the stock to the plants, because it is possible that it has a precipitate. Examine your jugs and labels[1]
The EC of the feed is lower than the calculated valueThe salt in the bag did not dissolve fully, and the stock has a concentration that is too low.Make sure that the salt dissolves fully in the stock. Calibrate the EC meter again.
Sludge after you put A and B togetherThe concentrates A and B touched each other.Discard the sludge. It is a precipitate and you cannot use it. Do not put the concentrates together.
The limits

Expected results and limitations

When you have the stock, the task for each day is to add the stock to the feed water and to apply the feed correctly. Read the coco and crop steering paper for information on the effect of the feed in the root zone. Read the irrigation manual for information on how to apply the feed.

References

  1. Guan, W. (2017). Fertilizer Compatibility. Purdue University Vegetable Crops Hotline, Issue 643. Purdue Extension. (source not from a journal, for example from a manufacturer). https://vegcropshotline.org/article/fertilizer-compatibility/
  2. Fernandez, D. (2020). Using Calcium Sulfate in Hydroponics. Science in Hydroponics. (source not from a journal, for example from a manufacturer). https://scienceinhydroponics.com/2020/06/using-calcium-sulfate-in-hydroponics.html
  3. LibreTexts Chemistry. Temperature Effects on Solubility (Physical & Theoretical Chemistry; Equilibria/Solubility module). (source not from a journal, for example from a manufacturer). https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_(Physical_and_Theoretical_Chemistry)/Equilibria/Solubilty/Temperature_Effects_on_Solubility
  4. Saloner, A., & Bernstein, N. (2023). Dynamics of Mineral Uptake and Plant Function during Development of Drug-Type Medical Cannabis Plants. Agronomy, 13(12), 2865. https://doi.org/10.3390/agronomy13122865
  5. Saloner, A., & Bernstein, N. (2024). Mineral nutrition for Cannabis sativa in the vegetative stage using response surface analysis. Frontiers in Plant Science, 15, 1501484. https://doi.org/10.3389/fpls.2024.1501484
  6. Powell, K., & Bauerle, W. L. (2026). Predicting vegetative phase nutrient uptake in Cannabis sativa L. via transpiration-driven mass-balance. Frontiers in Plant Science, 16, 1753553. https://doi.org/10.3389/fpls.2025.1753553
  7. Hultberg, M., et al. / van Os, E. (2004). Water quality assessment of different reservoir types in relation to nutrient solution use in hydroponics. Agricultural Water Management (Elsevier ScienceDirect). https://www.sciencedirect.com/science/article/abs/pii/S0378377404001908
  8. Yep, B., Gale, N. V., & Zheng, Y. (2020). Aquaponic and Hydroponic Solutions Modulate NaCl-Induced Stress in Drug-Type Cannabis sativa L. Frontiers in Plant Science, 11, 1169. https://doi.org/10.3389/fpls.2020.01169

The Cannabis White Papers · CC BY-NC 4.0 · version 1.2 · updated 2026-07-18