How often should I give new nutrient water to plants growing in DWC?
You can change your reservoir water for new nutrient-water every one or two weeks, but in the meantime they need to have the reservoir topped off with pH’d nutrient water at 1/4 strength. After a grow or two, you’ll notice that some strains (like BlackJack) will throw a fit if their water isn't changed weekly, while others (like Wonder Woman) are hardier and can handle a wider array of conditions.
As a general rule of thumb, you should completely change your reservoir at least once every two weeks in the vegetative stage, and at least once a week in the flowering stage.
Do I really need to check the pH?
Checking the pHcan be boring/tedious, but it’s also one of the most important factors in any grow, especially in DWC. Good pH management makes for pretty plants and bad pH makes for sickly plants. Think of pH adjustments like a supplement that makes your plants grow better and faster!
What are optimum nutrient levels for growing cannabis in DWC?
Always start with half of the recommended dosage on the schedule provided with your nutrient system. For example, I use General Hydroponics Flora Trio, so I just use the schedule on the back of the bottle divided by 2.
After that, dial it in! That means to watch your cannabis for signs of nutrient burnor deficiency. If it gets nutrient burn, reduce the nutrients from 50% to 25%. If it's becoming lime green and the pH is between 5.5 – 6.5, increase the nutrients from 50% to 75%.
Typical pH Levels
- 5 and below: Root Damage
- 0-4.5: Poor Nutrient Uptake
- 0-5.4: Good pH Level
- 4-5.8: Perfect pH Level
- 0-7.0: Acceptable pH Balance
- 5-8.0: Poor Nutrient Uptake
- 5 and Above: Root Damage
Note: Soil grown plants tend to need a little bit higher of a pH than hydroponics because soil retains and releases certain elements to your plants at different times. However, both hydroponic and soil pH levels should stay within the same optimal range of 5.5-6.0 pH.
Common PPM Readings
These readings reflect the PPM your water should have at a given stage of growth
- Seedlings: 100-250(nutrients aren’t really needed here, hence there’s not a lot of particles needed)
- First Half of Vegging Cycle: 300-400(this is usually after you transplant, which still don’t require many nutrients)
- Second Half of Vegging: 450-700(you’ll start giving your plants more nutrients at this stage)
- First Half of Flowering: 750-950(your plants will be eating more as they grow, so they’ll be taking in more nutrients)
- Second Half of Flowering: 1000-1600(this is when your plant’s eating the most, especially if you give it additives)
- End of Flower, Entering Harvest: As close to 0 as possible(this is when you’ll be flushing your plants, so you don’t want there to be a lot of particles left over)
For a quick fix when PPM’s are high
- just add a bit of fresh water with a good pH level and watch them drop. Filtered, pH’ed water is great when things get a little too much in your reservoirs.
When readings are low
- it’s usually time to feed your plants. When you add nutrients to your feeding solution your PPM’s will go back up, and when your PPM’s and pH’s are in balance your plants are going to be happy and healthy.
- Just remember that these readings need constant adjustment, so if you haven’t been keeping a close eye on your plant’s PPM and pH levels there’s not better time to start than now.