It can be tricky to know how often you need to add nutrients to your hydroponics system.
Different plants have different needs, and the type of hydroponic system that you are using will also dictate how often you need to feed them.
However, it’s agreed by most avid growers, that adding more nutrients every two weeks and flushing out your system every month or so is sufficient.
Below are some guidelines on which plants require more or less nutrient concentration and when I recommend adding fertilizer in order to keep a healthy PH balanced hydroponic water.
What is hydroponic reservoir maintenance?
Hydroponics is a subset of hydroculture. Hydroculture refers to growing plants in hydroponic water and in soiless media like perlite, rockwool or gravel.
The plant roots are immersed directly into the nutrient solution rather than being grown in an aggregate medium that has been saturated with it before planting.
So when people talk about reservoir maintenance, they’re referring to adding sufficient nutrients to the water that the plants are being grown in.
The concept of adding nutrients to a maintained water system is pretty simple – it’s just a matter of knowing which supplements you need, how much to use and when to add them! Let’s learn more about these things here.
How often should you feed hydroponic plants?
Feeding your hydroponic plants does vary, so it’s important to check the nutrient solution every time you add water.
If your plants are growing in a recirculating hydroponic system, then it’s best to feed them about once per week while they’re growing – more frequently when they are young seedlings or cuttings.
If you’re using the ebb and flow system, you should feed them about once every two weeks while they’re growing. Less often when the plant is flowering and producing fruit.
If your hydroponics systems have a drip irrigation system, it’s best to feed them no more than twice per day because too much fertilizer can cause salts or other harmful chemicals to build up in your hydroponics system.
How long do hydroponic nutrients last?
Hydroponic nutrient solutions will last for a few weeks to several months depending on the hydroponics system. Most systems such as ebb and flow or top drip irrigation use water that is recirculated, which means that nutrients are reused.
Check out our guide for buying the best hydroponic nutrient solution
Recycle systems tend to be more efficient with their usage of nutrients because they cannot leach out of the growing medium.
Nutrient solution is constantly added with these types of systems, so you will need to replace your solution more often than in non-recirculating hydroponics systems such as deep water culture or aeroponic where most nutrients are drained out after each nutrient feeding session.
Quick note: Your hydroponic solution will expire, that’s why it’s so crucial that you keep PH balanced water a priority. Nutrient deficiency is the leading cause of your plants growth.
Do you use nutrients every time I water?
Some people put more nutrients in every time they top off their hydroponic nutrient reservoir.
Other sources recommend using a timed release fertilizer, which has been pre-mixed into the water and will be released over a certain time frame to keep your plant growth more even. You can check our our top recommendations for the best hydroponic fertilizers.
This is especially effective if you’re growing in a greenhouse because you can cover the whole system and not worry about it drying out.
Quick note: Your PH levels should be checked regularly so you don’t accidentally burn your plants. PH levels should be measured on a scale from 0-14, with anything under seven being acidic and anything over seven being alkaline.
How often do you need to add nutrients?
That really depends on the nutrient you choose and how well your plants are able to absorb those nutrients.
It can take as little as a few days, but it could also be close to one month before there’s too much or not enough of something in your hydroponics system.
Also, don’t forget.
Adding nutrients is only part of the equation, you also need to make sure you flush your system fully to help the plant roots have the best chance of flourishing.
How often should I flush my hydroponic system?
Flushing your hydroponic system is important to avoid nutrient buildup. Nutrient buildup can lead to growth issues and decrease your yield.
There are many different ways you can flush your hydroponic system, including:
Water only flushing (no nutrients)
This is done by replacing the water in the reservoir with fresh water every few days or weeks depending on how often it’s used and what type of plants you’re growing.
Water only flushing with nutrients
This is done by replacing the water in your reservoir with fresh water and adding a nutrient solution to it every few days or weeks depending on how often it’s used and what type of plants you’re growing.
Deepwater Flush (DWF)
This is done by draining the nutrient solution to waste and refilling it with fresh water. You need to do this once or twice per week depending on how often you use your system, what type of plants are being grown, etc.
Recirculating Flush (RDF)
Fill a separate reservoir full of plain sterile water from the tap, and pump it through your hydroponics system. Do this once or twice per week depending on how often you use the system, what type of plants are being grown etc.
Flushing with hydrogen peroxide
Fill up a separate reservoir full of tap or distilled water from the source needed to fill your hydroponic systems nutrient tanks (or reservoir).
Add 3-4 drops of hydrogen peroxide to kill off any bacteria in the system. Let it circulate for about an hour, drain and refill with clean water.
Flushing with vinegar
Fill up a separate reservoir full of tap or distilled water from the source needed to fill your hydroponic systems nutrient tanks (or reservoir).
Add white vinegar to kill off any bacteria in the system. Let it circulate for about an hour, drain and refill with clean water.
See our full guide on using vinegar in your hydroponic system
Quick note: Your waste system is also an important part of your hydroponics system. Try to maintain it, to avoid any issues with nutrient buildup that could lead to growth problems from plant disease that starts in the plant roots during the growth phase.
A rule of thumb on topping up hydroponic nutrient solutions
To recap, knowing when to top up your nutrient solution depends on the hydroponic system you’re using and which plants you’re growing.
However, if you add nutrient mix every two weeks and drain the systems reservoir every month or so, you should be fine.
The frequency at which you add nutrients should be determined by the severity of any nutrient deficiencies or toxicity issues.