Maintaining a cool reservoir

One of the most frustrating things for me, being a hydroponics enthusiast in India, was (apart from the unavailability of stuff of course) the weather conditions in India. Any of my fellow growers would agree that every single bit of knowledge on hydroponics is generated in countries with weather temperatures a stark difference from what we have in India, or Pune at least. There were many times through my journey in hydroponics that I thought maybe the methodology is just not meant for us. But shake that thought away – there are ways to get around everything!

While most of us have no trouble maintaining ideal light and nutrient concentration conditions a common problem faced by people in hotter climates is the temperature of the nutrient solution. I won’t speak much about ambient temperature above the root zone simply because I would assume you’re either growing inside under lights; or a seasonal outdoor crop, based on the season of course.

How to keep that damn root zone cool.
Hold up. Open up your system and take a look at those roots. Are they slimy? Are they brown? Are they scarce? Are they white? Are you surprised at their growth?

I prefer hydroponics simply because of the results I see in the time I see them. I know something’s off when I check my roots in 3-4 days and don’t see abundant growth.

So if you’re roots are yellowing, browning, slimy or just not growing, it’s possible (and I say possible) that this could be due to the lack of oxygen in the root zone. A quick google search will tell you that if your nutes are above 30 degrees, they loose they ability to hold dissolved oxygen by half. Which means that your roots aren’t getting much oxygen AND that your reservoir is like a jacuzzi of bacteria, fungi and algae.

Here are a few tips I’ve tried and they work pretty well.

Bigger airstones

Get more dissolved oxygen in there. Use better quality bigger airstones. Remember that more oxygen dissolves in your nutes if more surface area of water is exposed to oxygen. In this case this translates into smaller, more bubbles will ensure more dissolution.


Wrap your reservoir tank with a wet towel. I know it my sound silly, but it works, specially if you’re looking for a small dip in temps like 1-2 degrees. I had a reservoir with nute temp at 31.9 degrees and 1 1/2 hrs later it had fallen by 2 degrees. Nice if you’re working with nutes around 24-25 degrees and want them just cool enough for that root zone.


The Americans call it Food Grade H2O2, we just call it 35% H2O2, here in India. This is high concentration hydrogen peroxide. Everyone meddling with hydroponics must be aware of the uses of hydrogen peroxide. For those of you who are new to this, hydrogen peroxide, when mixed with water, releases an extra oxygen atom that diffuses in the water, re-oxygenating it. Moreover, H2O2 prevents the growth of bacteria and other microorganisms keeping the slime of those roots. We usually get H2O2 in medical stores in India, diluted to 3%. This works too. Use about 1 ml per litre the first week and increase it by an ml. each week till you reach 3 ml. Personally, i wouldn’t go beyond 3ml per litre as it could be harmful to the rootzone.

Change your reservoir water at the right time

Here in india, with our overhead tanks, our water reaches high temperatures by mid day so remember to change your water in the mornings (preferably before 9am) rather than later in the day.


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