12 Hydroponic Problems and Solutions to Avoid Disaster
Hydroponics is not trouble-free. It requires technical skill to constantly monitor its performance and knowledge of when intervention is needed to maintain or improve it. Because after all, since you spend money to set it up and keep it running you need to ensure your investment is paid back.
Here I present to you 12 hydroponic problems and solutions that you should be aware of to avoid unnecessary disasters.
In any case, it is really important that you regularly check the health of your plants for any alarming early signs, the general condition of your set-up and the indications of the monitoring equipment you may have.
Be diligent and always take action to identify the problem before it gets worse; there will be a point in some cases where the plants cannot be saved. To make your life easier, it helps to keep a log (including photos) of the problem, your rectification actions and the result so that next time it happens you know what to do (or not to do).
So, let’s see which are the main issues you will encounter and what can you do to fix them.
1. Wrong or imbalanced fertilizer
Fertilizers for hydroponics are different to the ones for soil, as soil will have some elements already in it and has the ability to alter the chemistry (concentration mostly) of some added elements. Therefore the fertilizers for soil need to be compensating for the fact that some elements may quickly leach before the plant be able to absorb them or may be fixated to soil minerals (Singh & Schulze 2015). So their composition is quite different to the fertilizers for hydroponics.
Hydroponics fertilizers need to have ALL nutrients you will need (macro- and micro-nutrients) in the right amounts. Low concentration of one element below the required concentration for the variety and growth stage will lead to deficiency.
- Choose the right fertilizers designed for hydroponics.
- In addition, make sure that they are of the right mix of elements suitable for the plant variety and growth stage.
- If you are just starting, you can choose ready mixes in liquid form (but shipping may be more expensive as you are paying for water-based solution to be shipped and the respective concentration of elements in the solution can be restrictive).
- Alternatively you can buy two or three-part mixes (either solution or dry) which you can mix yourself in the right amounts.
2. Water quality
Depending on your area, tap water may be hard or soft. Hard water has high Total Dissolved Solids (TDS); of primary concern are the calcium and magnesium salts which you can measure with an EC/TDS meter. The dissolved calcium salts can attract calcium salts of your nutrient solution forming larger compounds, potentially leading to calcium deficiency.
More importantly though, high TDS / EC water will make it difficult to you to add nutrients beyond a level dictated by the target concentration of the nutrients in the solution (for the variety and growth stage of your plants).
The benefit of soft water (low TDS) is that you have flexibility adjusting your nutrient solution and still be within the EC/TDS levels. If you have the means, distilled water from an activated carbon filter is a way of reducing TDS.
Even better but more costly, is a reverse osmosis (RO) system which takes TDS close to nothing; but has lots of benefits long-term and will be paid back since you will not be discarding nutrient solutions as often.
Though if the cost was an issue, I would not go to the RO system unless my installation was for pure profit-making (eg professional set-up). If you are new starter in hydroponics you are ok with distilled water or even tap water if it is below 200 ppm.
3. Nutrient deficiency
(Read my post on 12 Plant Nutrient Deficiency Symptoms and How to Fix Them for more detailed information…)
Deficiency: when a primary macronutrient (elements) – Nitrogen (N), Phosphorus (P), and Potassium (K) – or a secondary macronutrient – Calcium (Ca), Magnesium (Mg), Sulphur (S) – or a micronutrient (trace element) – Boron (B), Chlorine (Cl), Copper (Cu), Iron (Fe), Manganese (Mn), Molybdenum (Mo), Zinc (Zn) – is in low concentration in the nutrient solution or is not absorbed efficiently, plants show symptoms of nutrient deficiency.
It needs to be said that usually symptoms will differ between the deficiency in different elements. Also other parameters such as low oxygen in the water solution or limited air circulation or diseases may cause deficiency symptoms that may differ from the usual or expected ones. So you need to ensure that parameters not relevant to nutrients are ok first, before you resolve the nutrient imbalances.
- Know what your healthy plant should look like
- Ensure that water is aerated, air is circulated above the roots and there is not a disease problem
- Measure the pH and the EC of the solution to determine if you are outside the range. Take action to correct pH first and then EC
- If the problem persists and you cannot balance the solution, flush it and make a new one.
- Suggestion is to use soft water, then add your correct amounts of your fertiliser and correct the pH and EC to the normal levels.
pH is the indication of how acidic or alkaline a solution is. pH impacts the absorption ability of the plants for the different elements. As a general guideline, if you keep pH level between 5.8 and 6.2 (slightly acidic) then you are fine. However if you want to be more accurate, check out the pH level for some specific plants in the table below.
You need to research what is the optimum tolerance levels for your plants and the different growth stages (sprouting, seedling, vegetative, budding, flowering, ripening).
It is crucial to measure pH when preparing a new nutrient solution or adjusting a solution (adding more nutrients, or adjusting pH with proprietary additives) and constantly thereafter.
pH meters are quite handy for this or at least having pH test paper and measure once a day.
5. TDS / PPM / EC
TDS: Total Dissolved Solids. Indicates the total quantity (and concentration) of dissolved solids in the water solution and is measured in PPM. Any source of water will have dissolved minerals and compounds. What makes this relevant to hydroponics is that adding nutrients in the water the TDS will increase. So using water with high(er) TDS will limit you into how much nutrients you can add. That is particularly a problem when you want to re-balance your solution. When the solution is already in high TDS you may not be able to add more nutrients as the indication will exceed what is the maximum for the particular plants you have.
EC: Electrical Conductivity. Indicates the concentration of ions in the solution and is measured in microSiemens per volume unit (e.g. μS/cm2). As water has ions of minerals and metals it conducts electrical current. Adding nutrients, which mostly are in the form of salts, they turn into ions in the water thus increasing the EC. So measuring the EC of your solution you can understand the nutrient concentration in it; and it is more accurate when you have used distilled water as by large the EC is a result of the nutrients rather than the pre-existing salts in the water.
The EC has a relationship with TDS. As we said TDS shows the total dissolved solids and EC the concentration of ions in the solution. Fresh water has dissolved solids, ions and other compounds; so only part of the TDS is the EC. In a nutrient solution, the more distilled the water is the stronger the link between TDS and EC because a larger proportion of the TDS are the salts (and lower concentration of the total dissolved solids and other compounds). That link is described by a conversion factor “ke”, so knowing one value you can estimate the other: TDS = ke*EC.
Usual conversion factors range from 0.5 to 0.8 or 500 to 800.
When EC is in mS use ke 500-800 and when EC is in μS use ke 0.5-0.8.
Unfortunately it is not that simple though. Different salts can have different impact on EC: at a given TDS of say 1000ppm salt A could be raising EC by 1 microSiemens while salt B by 2 microSiemens.
And of course the temperature of the solution is key. The warmer the solution is the higher the EC indication will be.
In addition the way the solution is fed to the roots plays a role in the required concentration. Growing media which can buffer nutrients (such as coir) require higher concentration of some nutrients compared with techniques like Aeroponics or NFT where the solution is directly fed to roots.
Fancy reading more? Here are some easy sources of info:
- Use distilled water for more representative indications of TDS and EC.
- Note down the TDS and EC of the fresh water you used to make the nutrient solution. This will give you an indication of the real TDS and EC of the nutrients you added.
- Know your specific plants’ needs at the growth stage they are in: what TDS and EC they can tolerate. Young plants need low concentrations.
- Monitor the solution temperature and know what the EC indication should be for that temperature.
- Know the ke conversion factor of your TDS meter if you are using one. A TDS meter is essentially an EC meter which converts the EC measurement to TDS using a built-in conversion factor which can be different across different TDS meters. So perhaps use an EC meter anyway.
- Look out for the recommended nutrient concentration in microSiemens or ppm for the nutrients you are adding (most nutrient mixes clearly state those on the label).
- Do not add too much nutrient in your solution all at once. Especially with the ready mixed solutions which are concentrated, a bit of nutrient can change the EC more than you expect. So be slow in this process and make sure you stir well while you do that. If you exceed the required level, add water to dilute.
- Do not add nutrients all in once to make a solution; add them diluted one-by-one. So dilute one in a separate container until you reach the recommended EC level and empty the container in the bigger water reservoir. Then go to the second one and follow the process. Which one goes first, second and so on, will be based on charts given to you by the manufacturer of the nutrients.
- Adding more nutrients in a working solution already being fed to plants needs to be slow as sudden changes can shock the plants.
Νo light, no photosynthesis. Poor light distribution, low light or incorrect wavelength, too much heat emitted from the lights and incorrect photoperiod (light duration) can lead to poor growth, or weak stems or no poor flowering and worse no growth at all.
So lights are VERY important. Light needs to meet certain characteristics depending on the growth stage of the plants. Spectrum, intensity at different wavelengths, efficiency, as well as the positioning of the lights relative to the plants and the resulting light distribution are parameters to carefully look at.
I will not go into details here on the physics behind all the above parameters and how they impact growth, but please note that if you overlook lights you are not going to receive satisfactory yield (if at all).
Good source of information, if you are curious, can be found Urban Vine.
- Do your research in lights. My recommendation is to go for high efficiency LED lights, but do not go for cheap ones, as you may need to replace them soon.
- If you are on a budget, you can go with fluorescent – that is fine too.
- Better to have bright lights than low and unevenly distributed light.
- Remember to lower the lights closer to plants as they start flowering and making fruit (they need more light at that stage).
- Don’t focus on the wattage of the lights; watts mean very little as different technologies will give variant light intensity and spectrum for the same watts. Instead, focus on the metric that measures light output such as PPFD – photosynthetic photon flux density. It is measured in micromoles per square meter per second (μmol/m2/s). Indicates the instantaneous PAR (photosynthetically active radiation) that falls on an area of 1m2 every second.
- PAR and PPF are related: PAR is in (μmol) and PPF in (μmol/s).
- For more information you can start from Wikipedia or Light Science Technologies.
- Ensure light is evenly distributed on the plants canopy. Especially important with LEDs, as LEDs tend to be more focal than other lights.
- I would suggest you do not follow the rules of thumb that involve watts for the reasons explained above. Instead, know the PPFD value for your particular plant at every growth stage.
As a rule of thumb with PPFD follow these values from :
- Microgreens: 70-140 μmol/m2/s
- Leafy greens (eg lettuce): 140-200 μmol/m2/s
- Fruit-bearing (tomatoes ,peppers etc): 170-460 μmol/m2/s
Allow for lower PPFD values for when plants are young and move up as they grow and/or start flowering and forming fruit (where applicable).
Temperature of air and water is important in order to stimulate growth and maintain healthy plants. Lower or higher temperatures that the ideal can affect the plant’s ability to absorb nutrients, to produce quality and tasty fruit and to fight against pests and diseases.
For your information only, in some plants that will most likely not be suitable for indoor hydroponics, such as olive trees, lower temperatures are necessary for turning flowers to fruit.
Roots are quite sensitive in temperature. The outer layer of cells can get damaged and root growth slows down having knock on effects on the plant’s health and growth.
On the other hand, heat stress caused by air temperature above 86 degrees F (30 degrees C), may reduce the ability of the plant to take up more water to survive. That is complex though, as the EC level (electrical conductivity) plays a role into the absorption of water. The higher the EC the more difficult it is for the plant to absorb water, critical at higher temperatures.
There is no blanket rule of thumb for all plants when it comes to water temperature. It differs between the plant species. For example, lettuce and other small leafy plants have optimum water temperature at 68F (20C) (Sakamoto and Suzuki 2015), potatoes like it at 77F (25C) (Chil et al. 2001), cucumbers a bit higher at 82F (28C) (Daskalaki and Burrage 1998) while others like onions have a much higher upper limit at 84F (29C) (Rahmat et al. 2019).
HOWEVER, you need to remember that the upper limits sited above are under a controlled environment. The higher you go in water temperatures when the upper limit is relatively high the more likely you are to induce the growth of pathogens which may hinder yields (see Panova et al. 2003).
With that in mind, you need to aim for water temperature of 66-70 degrees F (19-21 degrees C) and definitely not exceeding 75-77 degrees F (24-25 degrees C). If you want to be very accurate, keep the water temperature at 68-70 degrees F (20-21 degrees C). Also, below the lower temperature limit roots slow down in growth and functionality.
Do not have the root zone too low or in contact with the floor where the colder air tends to stratify. Unless of course you have a fully controlled environment with heated and circulated air in a grow room.
Air temperature should not exceed 86 degrees F (30 degrees C) an should be circulated to prevent air stratification and to allow for higher respiration rates so that plants can absorb more water to survive.
At high air temperature:
- dilute the nutrient solution to lower the EC level so that it is easier for the plants to absorb water
- reduce the air humidity level to prevent diseases and pests to thrive.
Leaking pipe joints, valves or growing beds, clogged up tubing (eg in NFT systems) or cracked nutrient tank are all cases that can happen. They lead to loss of nutrient solution which costed you money and potential corrosion in parts of the system. Above all, it can lead to plant stress if it the lead significantly drains out the system and it goes unnoticed.
- Always check the area for leaks – great indication is if water is dripping from somewhere. The leak may though not be exactly where you see the drip, so investigate.
- Check the system for root growth and take action when roots start clogging the tubes or are too big slowing down the water flow.
- Ensure that your nutrient solution tank is dimensioned to hold all the volume of the solution running around in pipes etc.
- When you build a system make sure that you pressure test it before adding any nutrients in it. Just water circulated with the pump is good to test for leak in the beginning. If you see leaks, tighten joints, valves etc and re-test.
9. Pumps, Nozzles and Air Pumps
Important to make sure that all components that provide nutrients to the roots are working properly.
Pumps can fail due to an electrical fault but more frequently they can get clogged up by algae growth in the impeller casing.
Nozzles get clogged up as salts build up.
Air pumps, like water pumps, can fail due to an electrical fault.
Failing pump or clogged nozzles will lead to plant roots drying out and if it is prolonged it can lead to plant damage.
Air pump failure can leave the nutrient solution and consequently the roots without enough oxygen (for some hydroponics systems such as Water Culture, Ebb & Flow and Nutrient Film Technology are particularly susceptible).
- Observe for abnormal noise coming from the water pump. It may be that algae have grown in the impeller casing – so clean it.
- Regularly clean the nozzles and the air pump stone.
- Design your system so that some water can be left there to touch the roots so that plants do not get stressed until you fix the issue. For example, in the NFT system have the water drain pipe inlet raised above the bottom so that some water accumulates.
10. Growing medium
For some types of hydroponics the growing medium is the plant’s main support and works as the absorbent of the nutrient solution. So it is important.
The wrong type of growing medium, e.g. a less absorbent one, than what is really required, will “starve” your plant from water and nutrients and will lead to plant stress. A more absorbent one may lead to root rot and eventually to plant death if no action is taken.
Another issue can be algae growth in the growing medium which can reduce the oxygen level in the solution and alter the solution chemistry and lead to nutrient deficiency.
Ensure you know which type of growing medium is most suitable for your plants. Consider:
- Absorption and water retention ability
Choose wisely based on the above and ensure that if you reuse the growing medium clean it thoroughly before using it again.
11. Flushing and refilling
Leaving it too long between flushing and refilling the system can lead to the following problems:
- Nutrient deficiency as the plants will have used up nutrients. Problems of nutrient deficiency are explained above.
- Growth of pathogens in the nutrient solution that will lead to diseases
- Well…sorting out the above problems if you want to save your plants.
As you can understand, resolving problems related with nutrient deficiency and diseases is a lot harder and sometimes impossible compared with more frequent flushing and refilling.
Aim for regularity, every 2 to 3 weeks between each flushing/refilling. This way you can have higher yields with less problems. You will be spending less time to fix problems and become more experienced in the process.
Tight spaces which would not allow you to work around your plants with ease or very cold or hot spots will require you to take extra measures for a controlled environment. Proximity to a water source and drain (the nearest tap and drain) is equally important to make your work easier and less messy.
Ensure that you consider the position of your hydroponic set-up:
- Allow for adequate space for you to move around your set-up
- For indoors, chose a spot indoors that is neither too wet/cold neither too hot
- Having a water tap and a drain near your set up will help you with the flushing/refilling as well as prevent major hassle if you have a leak.