Maintaining your hydroponic system


Hydroponic System

Clean the grow room beforehand. Also, before setting up your system and putting it back in the grow room, clean the plant box well with a 10% bleach solution. Always cut off dead leaves and remove them from the grow room. Decaying organic matter attracts fungus gnats. You should also remove diseased plants, so the infection does not spread. When you change water in your reservoir, wash the tank well with a 10% bleach solution. If you use big trays for your blocks & slabs consider washing these too, especially if you have had a problem with root rot.

Hydroponic System


If you use a drip system buy a few extra drippers, so you can change drippers if any are clogged up. Have a bucket with vinegar in your grow room and throw the clogged drippers in, so they will be cleaned.


Hydroponic System

We recommend that you get a timer which can be set at 5 minute intervals, so a full cycle will only soak the stone wool for 10 minutes. To avoid salt built up we suggest that you top water your plants once per week. Use the same solution as in your reservoir. Do not top water with plain water (it will shock your plants). Also be sure to have a tray with deep enough grooves so that water drains away from the GRODAN cubes/slabs.


Hydroponic System
  • Never go below pH 5 or the stone wool may be damaged! Below pH 5 and higher than pH 7 the plant cannot readily take up nutrients.
  • 1-2 hours before planting, don't forget to saturate the stone wool with pH 5.5 water.
  • Flush GRODAN with your nutrient solution at pH 5.5 and drain to waste and then put the GRODAN in your system.

The pH in your reservoir will go up during vegetative growth- it is a natural response - it means your plant is growing! But also higher temperature and algae growth in your reservoir will cause pH to go up. So keep an eye on pH. For most plants, the reservoir should be around pH 6.0


Please down load the blue leaflet “Watering and pH” . This leaflet is also available from your local retailer.


We recommend that you completely change the solution once a week. Yes, you can top up the reservoir and adjust EC/pH, but your solution may be out of vital micro nutrients or be infected withPythium (root rot). If your reservoir contains ready to use (diluted) nutrient solution, please use phosphoric acid (pH Down) or lemon juice to lower pH.

Remember: If it is not broke, don't fix it !!


Consider keeping a journal that lists: the EC, pH, temperature, CO2 & light level each day. This way you can learn from your own mistakes & successes. Records like this also make it easier for the shop to answer your questions when you have a problem.


Hydroponic System
Ca deficiency in leaves.

Before you blame your plant food for unhappy plants, check your journal. Everything must be in balance. Change one parameter at a time and look for the effect. A common problem is that the reservoir water is too cold. Consider putting a heating element in the tank (to 70ºF) or put heating mats under the GRODAN. If you have trouble getting the plant to set flowers/fruit try to make a greater difference between night and day temperature. If that is not enough, increase CO2 injection during daytime.

COMMON PROBLEM: Calcium deficiency

If the youngest leaves are curled downward, more than likely it indicates a calcium deficiency. If old leaves are curled; something is probably wrong in the root zone (which also reduces the calcium uptake)

Calcium deficiency is the result of insufficient water movement through the plant. Remember, calcium only travels in the water stream of the plant, not in the nutrient stream. Therefore, calcium deficiency is usually (90% of the time) related to the climate in the growing area. High humidity will prevent calcium uptake even if there is sufficient Ca in the feed solution.

Hydroponic System
Ca deficiency in fruit.

Also, large day/night fluctuations in humidity will disrupt the Ca flow within the plant and lead to blossom-end rot (BER). Another cause of BER or obvious Ca deficiency in the leaves is poor root development. This is a result of low substrate temperatures or the presence of a root pathogen such as Pythium or Phytophthora. Calcium is taken up by the area of the root immediately behind the root-tip. If the roots are not actively growing, new root tips will not be formed and consequently, Ca uptake will be reduced. 


Make a habit of taking a close look at your plants every day. Do they look perky? Look for leaf color, leaf shape and bugs, then update your journal. If you catch a problem early it can be fixed!

Take the advice of friends and other hobbyists with some caution. What may have worked for someone else may not work in your growing condition. Experience is the best educator.