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Water temperature ranges in hydroponic systems

Why do we need to control water temperatures?

In a natural environment cannabis does not thrive submerged in water: it prefers alternate wet/dry climate (which we replicate with the wet dry cycle when growing in soil or coco-perlite) in order to drag oxygen into its root system and thereby into the plant.

However when we start to adjust the natural order with an indoor grow room, and especially when using the highly artificial hydroponic method of growing cannabis, the plants’ root system needs careful manangement. If you plop a cannabis plant into a bucket of water it will die if left for a few days. This is because the root system will be unable to perform osmosis, and, deprived of oxygen the plant will be unable to photosythesise and eventually it will wither and die.

(so why do cannabis growers use hydroponic systems? Quite simply because given the right conditions, hydroponics enable bigger, quicker results than any others. Hydroponic grows “mainline” the nutrients, water and oxygen direct to where the plants can make use of them: the root system).

When growing with hydroponic systems there are a number of different ways to introduce oxygen into the system. The main examples are:

  1. DWC (Deep water culture)With DWC the oxygen in the system is introduced mechanically through an air pump and air stone underneath the root system.
  2. EBB & FLOW.The tray is flooded periodically, submerging pots filled with ceramic pebbles. As the water drains through, it drags all the old oxygen out of the sytem and pulls in oxygen rich enhanced new nutrient.
  3. NFT (NUTRIENT FILM TECHNQUE)This is a system where a film of water is passed over a tray where the roots sit on a spreader mat. As the roots grow some sit submerged and others arch out of the nutrient film to reach air in a highly humid, light sealed enviroment. Some growers will also add an air stone to enhance the oxygen content within the main reservoir and thereby the film of water. Dependent on the height of the trays in relation to the reservoir tank, the fall of water from the tray back to the tank can also introduce oxygen.
  4. DUTCH POT / BATO BUCKET SYSTEM – read this article here and follow WildWW’s grow here

 

 


Botanicare AquaShield – Gallon

This chemical anti-fungicide is very effective against pythium.

If you can’t run to the dollars to buy in a chiller, AquaShield is the next best thing. Growers swear by its effectiveness and ability to stop the spread of root rot within a hydroponic system and at the same time encourage new healthy root growth.

its been two days with this in the res and we are talking a full 180, new roots exploding through the old gunky ones. … i wont fill my res without it …

 

 

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So why am I talking about oxygen when the subject matter is water temperature?

The temperature of water and its oxygen content are closely related, and the temperature of the solution needs to be fairly closely monitored in order to maintain dissolved oxygen levels. At low water temperatures, the plants go into shock, but as the temperature rises in the tank the solution loses the percentage ratio of its oxygen content. Here are some figures:

 

tank temperature & % of oxygen in the solution (ppm) water temps

10ºc (50ºf) 13 ppm

20ºc (68ºf) 9-10 ppm

30º (86ºf) 7 ppm

As you can see the oxygen content in the resolution approximately halves for every 10ºc rise in solution temperatures.

ok got that! :)

In easy terms, ideal temps are between 18 and 20 ºc and if your water temps are anywhere near 25 -30ºc then the oxygen levels can be as much as half of the desired levels.

In easy terms, ideal temps are between 18 and 20 ºc and if your water temps are anywhere near 25 -30ºc then the oxygen levels can be as much as half of the desired levels.

BUT

As a direct result of the water temperature being at higher temps the plants will need more oxygen at the roots so the problem is almost squared and there is 25-40 % less oxygen in the solution and the plants will need double the amount than normal.

The real terms effect is that the oxygen level in the solution is only at 25 % of the desired levels and you can chuck as much light or feeds at them as you like but if they are only running at 25% of the required dissolved oxygen levels then this is hardly conducive to happy healthy growth is it?

 

 

Some of the results of low oxygen levels in the rez tank are:

  1. roots are unable to work effectively, leading to:
  2. a build up of toxins meaning that the plant will be unable to take up the water and feeds needed for healthy growth
  3. The whole plant begins to deteriorate as photosynthesis and carbohydrate rates slow leading to wilting.
  4. Leaf damage and root die-back. Ethylene is released and causes a toxic overdose and the roots fail.

 

And all of the above cause ideal conditions (especially in warm water) for every hydroponic growers worst enemy: 
PYTHIUM

 

 


Aqua Euro USA Max Chill Aquarium Chiller $395.95

 

So of course the real solution to high water temperatures in a hydroponic reservoir is a water chiller. We tried inserting bottles of ice water into the res tank but despite dedicating a small chest freezer to the production of ice, found it almost impossible to sufficiently and consistently cool our water (warmed by hot sunshine on the pipes outside). Its yet another expensive piece of kit to add to the grow room, but if you are growing hydroponically in an environment where water temperature rises either due to external environment (like ours) or internal environment (the tank is warmed by heat thrown out by your HPS), then a water chiller IS be the only solution.

This great chiller features:

  • digital display
  • titanium heat exchanger
  • super quiet operation
  • powerful compressor

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Aqua Heat Titanium Heater 300 Watt $31.00
And of course if the problem is that your water temps are too low, then its worth investing in a water heater to maintain a healthy temperature:

 

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