Can water be too cold for hydro?

[coldcanna]

So the new grow space is in the basement which is cold most of the year, the room itself will be climate controlled for the plants sake but I was thinking if I put the rez outside in the unheated area I could avoid buying a chiller. I was wondering what the lower threshold for water temps is in a under current or UC type setup?

 

[fatigues]

There is a diversity of opinion on this.

Most growers aim for 60-66 F for their rez water. Most is not all, however. In B.C., the practice by many indoor growers of BC Bud is to deliberately chill their res water to the mid to high-40s.

However cold your basement concrete is (my guess is 45-64 degrees during the winter in New England rock/soil) depending on your foundation depth) I would think that you would be fine taking this approach.

 

[jammie]

growth slows SIGNIFICANTLY below 65 degrees. oxygen saturation is best at 66-68, so its best to keep temps above 65 and below 75ish.

 

[coldcanna]

Thanks for the input guys...

Fatigues- That's very interesting I hadn't heard about the BC guys, or anyone for that matter, chilling their water that low on purpose. Is there any specific logic behind that? For me it just makes sense to let the natural cold take care of chilling for me, it seems silly to pay for the electricity of a chiller at the same time your outside air is sub zero.

Jammie- The 65-75 range is what I've seen as the commonly held knowledge for hydroponics, however I have found a couple scientific resources that say that the DO levels actually continue to rise all the way down to freezing... Check it out below-

http://www.dnr.mo.gov/env/esp/wqm/DOSaturationTable.htm

It is apparent that very cold water does indeed have more oxygen, but it is still a possibility that the cold might have some other adverse effects on the plant

 

[jammie]

hey there cold- interesting chart. i think 68ish is the sweet spot, high enough for vigorous growth but low enough for higher DO and root rot suppression. i do 5 gallon dwc so lower water temps may work for other types of hydro. i do a winter/spring grow in my basement where the temps are mid 50's before my 1k lights bring it up to low 70's but the nutrient solution usually stays in the upper 60's because of the cold floors

 

[overbudjet]

I run mine 65/68 with good result

 

[fatigues]

Fatigues- That's very interesting I hadn't heard about the BC guys, or anyone for that matter, chilling their water that low on purpose. Is there any specific logic behind that? For me it just makes sense to let the natural cold take care of chilling for me, it seems silly to pay for the electricity of a chiller at the same time your outside air is sub zero.

I have no idea why that temp is used by some of the growers in BC. My best guess is that it is because more dissolved oxygen = better. And yes, colder water allows for more dissolved oxygen. That's why the extremes of the North and South Atlantic are so rich in sea life, algae, krill, etc. There would be no other good reason to do it, AFAIK.

Personally, I would aim for 66 degrees. But the point to take away is that if it goes colder than that - which I admit is very much against established practice - it would appear that there are some who do so without any negative consequences and who appear to enjoy some benefits from it (at least anecdotally).

It might be that your best approach would be to put your rez on the floor, wrap it in Reflectix and see how it goes. If things look to be going iffy for you, throw am aquarium heater or three in there and try to get it in the mid-60s.

 

[coldcanna]

Good ideas fellas, this has the makings for a good side by side experiment. Jammie I'm in a very similar situation as you with a cold concrete basement, I'm guessing the HPS lights will prob keep my room in the high 60's low 70's so I'm confident that high rez temps will never be a problem. Hearing that some guys run there water much colder with no adverse affects is great news and solves my initial concern. It makes sense when you consider that plants' roots naturally grow deep into the ground where soil temps are cooler. Check out this map:

http://www.greencastonline.com/tools/SoilTempMaps.aspx

Granted people grow outdoors pretty much everywhere but lets just use northern Cali as a baseline because its the hub of growing in out country. Soil temps and therefor root temps are between 50-60 degrees.

 

[Hydrolized]

I run my cloner and veg systems at 75F, and my flower systems at 68. My logic is based on some university studies I read that stated optimum root growth temp is 78F, and total harvested dry plant matter started to decrease when temps were brought below 70F (this wasn't for MJ but similar C3 plants)...the only reason we keep it lower is because of the higher DO and most diseases/viruses commonly found in hydro systems tend to not like the cooler temps along with the higher DO. If you had a completely sterile system with no possible contamination vector (pretty much impossible) running your res temps at 78F would be best IMO.

 

[coldcanna]

Thanks for the input Hydrolized, I hadn't heard the 78 figure before. After everyone's input I believe I'll keep the rez within the climate controlled zone but ON the concrete floor to help add a cooling effect to the water. Thanks for the help gents!