With summer coming up fast, an important topic that often gets overlooked that any grower who keeps a reservoir must deal with; reservoir temperature.
For those who use true hydroponic systems, such as Deep Water Culture (DWC), or keep a large reservoir of nutrient solution, it's important to maintain your solution within a specific range to avoid major plant health issues arising.
The optimal temperature to keep your nutrient solution at is between 17℃ (63℉) to 22℃ (72℉).
If a reservoir's nutrient solution temperature drops below 15℃, the plants growth will retard and eventually halt all together until temperatures rise. The upside of having a cooler reservoir temperature is the potential for increased dissolved oxygen, but to utilize this you need to stay above the 15℃.
If a reservoir's nutrient solution temperature rises above 22℃, the plants access to dissolved oxygen will decrease, leading to a significant rise in anaerobic pathogens, such as Pythium (Root Rot), which is all too common in warm reservoirs, eventually killing your plants if unable to control. Most people can get away with few hot days here and there, even if your reservoir hits up to 30℃, but anytime you hit high temperatures, you always run the risk of pathogens overtaking your roots.
Another common side effect of having a hot reservoir leads onto nutrient concentration; if your reservoir becomes too hot, its nearly always a product of a hot environment. If your environment is hot, your plants will need to cool themselves via perspiring, which will result in your plants drinking significantly more water than usual, and in most cases, drinking only water, and not nutrients.
For those running in Deep Water Culture systems, this will increase the nutrient concentration of your reservoirs as the water is removed but the nutrients remain, increasing your EC/PPM. If your solution loses water at a significantly higher rate than losing nutrients, your solution runs the risk of becoming too concentrated and burning your plants, eventually leading to a complete nutrient lock out and serious plant health problems.
Avoid the gamble, chill your reservoirs!
Cooling your reservoirs
With summer just around the corner, we're going to take a look at options to cool your reservoirs down.
By far the most effective way to cool a reservoir: A Water Chiller.
While this method is the most effective and reliable, its also the most expensive, as water chillers for either Hydroponic or Aquarium use can set you back a few hundred dollars at least. Depending on your growing location and climate, this may be your only option if you wish to grow through the summer months with any real significant reservoirs.
Insulating your reservoir
This method is highly recommended for anyone needing to lower reservoir temps, as this technique can and should be implemented along side with any other method for keeping your temperatures down. Simple and cheap adjustments, such as painting or wrapping your reservoir in Mylar or white reflective surface covers can drop your temperatures down for very little cost.
Increase your reservoir size
A smaller reservoir will heat up significantly faster than a larger reservoir, as more water will take longer to heat, and vice versa. With good insulation and a large reservoir, it should buy you some more time to get through a hot day without as much of an increase in temperature, although this isn't always an option for everyone and posses some other potential issues for having a huge reservoir.
Remote reservoir location
Some growers will store there reservoirs away from there grow space, in a room or area with much greater environmental control, pumping to and from this room, to their grow space. Some growers will even go to lengths such as burying this reservoirs unground as a natural insulator, although these are not always an option for everyone.