Reservoir temp issue

Hey all!

I built a nutrient reservoir, auto watering, drain to bucket system. Everything works great! Only issue is that, I can’t keep the temp in the reservoir down between 65 - 70 degrees. This is causing the PH to change too. Since I use Advanced Nutrients Perfect PH for coco, this PH change has become a problem as well. My 2 stir pumps are the cause for this temp change. They raise the temp! But, I need my nutes to stay mixed very well together. My effort to control the temp started out with small frozen water bottles. I have now started to use the 1 gallon water jugs, frozen hard as a rock. I even bought an inexpensive transmission cooler from Amazon. Set that up to have the nutrients pumped through it with a 120mm fan blowing on it. Didn’t work. This is a real PITA!

To those that have a reservoir . . . . . what cooling system have you designed/made that works??

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An appropriately sized aquarium chiller will do what you need but they are spendy, might look for a used one on craigslist.

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@Hellraiser … Yeah, I’ve looked at those on Amazon. The cost is about $130.00 or so, not a problem. My reservoir is a 15 gallon, but I only fill it to 12 gallons/45 liters. Not too sure if a chiller like those will be able to keep the temp down.

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Be careful as there are 2 types of aquarium chiilers on amazon. The cheaper ones are kind like what you made with the transmission cooler and won’t work very well for your needs, the more expensive ones with a compressor is what you want and they cost much more.


@Hellraiser … those water chillers in the box cabinet on Amazon, are only a small radiator and a fan, in a metal box. I don’t think those will chill a 12 gallon tank.

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Yep, those radiator/fan coolers won’t bring temps down where you want them. You’ll want one with a condenser like this, rated in HP.

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You’re not looking at the right chillers:

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Hello @Myfriendis410 …I have a large system that I built for hydro…3, 45 gallon totes. Just coming upon heating issues…question…is the yield increase from the system worth the $700 for the water chiller I now need?

You are the only one who can decide on that. All I know is every diy method I’ve seen is a PITA and kind of negates the advantage of a hydroponic system: check once a week or so. Can’t do that if you’re trying to keep rez under 70F all the time.

One grower here bought a used apartment/dorm refrigerator, put a Homer in it full of water, built a copper coil to immerse in it and an cheap pump. Even that is nowhere near as good as a salt water aquarium chiller.

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@Myfriendis410 I was referring to this entry level aquarium chiller. These guys are saying that it chills a 10 gallon fish tank down to the mid 50’s.

Cooling Probe

I also looked at the chillers that you are showing too. I have ran the gambit, as they say on my options. Some of those are just a metal housing that holds the radiator part & fan. I just want to know, what will absolutely, chill the nutrient solution and keep it chilled with no problem. Only 1 REAL issue that I can see happening is, if it has a design like a radiator with small tubes for the fluid to flow through, just like an automobile, then they are prone to plugging up with what ever particles may be in the nutrients that you are using.

I have that 1/4 horse Active Aqua chiller: stainless steel interior lines, very large diameter, a small submersible pump is used and it pushes through slowly enough to chill, with a thermostat. You can also use an inline pump and rig it as a heat exchanger to push cold liquid through tubing in your rez. I just pumped from rez to chiller and back, continuously. It will hold to ± 1degree F.

I’ve seen a ton of hydro growers go through this (myself included) and it just ends up better to buy a chiller. This is assuming you have done every method of passively reducing the heat load on your nutrient solution.

@Myfriendis410 Yeah, I’ve tried a lot of things to date. I’m a MacGyver kind of DIY’r and not afraid to try off the wall ideas. For a 15 gallon tank only being filled to 12 gallons/45 liters each time, do you think I need a 1/4 hp? Seems like over kill for my setup. What do you think of this one?
Poafamx 16gal Aquarium Water Chiller 60L Fish Tank Cooler

Also found this one too! Like the one you have, just a little smaller. But I think it good for my 15 gallon tank.

Active Aqua 1/10th HP Hydroponic or Aquarium Chiller 2018 Model

When I bought mine it was $10 more than the 1/10th horse. I would also look at working with a larger standing rez if you can: makes you more stand alone: I ran a 30 gallon for 3 plants in a garage in SoCal so needed the cooling capacity.

Now I did have a thought before buying the chiller: right on the other side of the garage wall my grow space was located was a narrow strip of dirt (on my side of the property) with nothing growing but an orange tree from the neighbors house kept that spot shaded full time. I had the idea to bury a copper coil about 4’ down in a hole and circulate something like a methanol/water solution (keeps liquid sterile) and set up as a heat exchanger. I’m sure it would have worked.

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@Myfriendis410 … That’s funny you mention So. Cali. I’m born & raised there in Bellfower, Ca. Grew up in O.C. Went to Corona in 78. Lived in Riverside, Fontana, then finally Victorville in 2015. I retired in 2013 from VONS where I was a truck driver. Came here to N. Carolina in 2017. I presently have the same setup that you did in Cali. In my garage, along the wall. AC inside the tent. I don’t run more than 2 plants at a time now. Did 7 once, but it was a ton of work. Now, 2 in scrog is enough. The 12 gallons is plenty for the 2 of them. Since I’m retired, I can monitor the system like a hawk.

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The thermoelectric you linked above will cool water, but maybe not to extent you are trying. Fish aquariums don’t typically have the heat in them that a grow space will.

I built one using a peltier device and oversized pin heatsink with pc fan. Not sure if you are familiar with how the cooling devices work, but they basically have a hot side and a cold side. The faster you get rid of heat on the hot side the cooler the cold side will be. My concern about probe style you linked is that the heat will be close to the cooling probe and cause some of the heat to recirculate back into your solution. Imo a heat exchanger located away from the res and an external pump circulating water from res to cooler would work better.

Unless you have majority of stuff laying around, probably not worth the cost of trying. Sourcing all the components on large enough scale to make work would likely be close to wash on chiller. I spent $40 and recycled about another $40 worth of stuff, but it successfully cooled my 1 gallon aerogarden res.


@dbrn32 … I’m going to buy the chiller like @Myfriendis410 recommended here. Only I’ll get a smaller version to fit my setup. I looked into some heat exchangers, but I think the chiller is best for me. Thanks for your help.


I took @Myfriendis410 advise when I started but I only have 22 gal total so I bought the 1/10 hp. Works great.
Myfriend, have you seen the prices of those lately?? Sheeeezz! :scream:

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@spyonyou . . . it’s not that I just started, it’s because I switched from soil to coco coir 1 1/2 years ago. Got tired of watering 4 times each day, so I built a '15 gallon reservoir, automatic watering - automatic draining system, and I’m having trouble with the temp in the res warming up because of the stir pump. Temp goes up, and the PH changes. THIS, is a major problem, as I am using Advanced Nutrients PH Perfect for coco, and right out of the bottle, this stuff is, well… perfect. My chiller purchase yesterday, will take care of the issue. And the 1/10th is also what I purchased.

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Hey brother, I’m there with you. That’s why I got away from coco.
Trust me, it’s a great grow medium to grow in, but I didn’t want to water every day.

I have a 13 gal res and two 20 gal totes to grow in, one plant in each tote. I’m using Jacks, and I’m just gonna tell you, it doesn’t get any easier.

Absolutely loving my setup right now.
Good luck with everything! :+1:t2::v::sunglasses:

@spyonyou . . Well, I’m never going back to soil, period. Coco Coir is fantastic, with an automatic water & automatic drain setup. All I have to do is, fill the res and drain the waste bucket. Now yes, right now I’m doing a little more work cuz of the temp issue. But, That all goes away when that badass chiller gets here. Then, it’s back to fill res once a week and drain waste bucket every other day. I water 5 times (Fertigation) per day now on 1 plant, in scrog. Ran as many as 7 plants in my tent last summer. Too much work! One big ass plant is more fun, especially if it’s a photo & you top the heck out of it.

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