Cold weather cycling

[Jeremiah Robinson]

I have an aquaponics setup that I'm going to fill up with water this week, and I'm worried about the cold on my bacteria.

I'm in Wisconsin, in a greenhouse.  The tanks are quite well insulated and heated, so I have no worries about them getting too cold.  But the grow beds are sort-of inherently exposed to the cold, even with insulation on top and all around.  Heating them would be expensive and complicated.  Flooding them with warm water once an hour will keep them warm-ish, but it will produced large temperature swings.  I'm guessing it'll fluctuate between 80 and 60 each hour at night, maybe more on those really cold nights.  What effect will this have on my bacteria?  Will it survive?  Can I cycle in conditions like this?

[Alex Veidel]

I don't think it will be too much of a problem, as long as your water is warm. The lower temperature fluctuations might slow it a little, but overall you should be okay.

[Vlad Jovanovic]

Yeah, you should be just fine...Your low temps are about what my high temps were, and things cycled just fine. Maybe a tiny bit slower, but just fine nonetheless. 

If you have a way to run things (while cycling) constant flood/constant flow, that would probably go a ways in helping your grow beds to not act like a cold sink. It would offer some temperature stability and probably save you a bit on your heating bill...but either way, at the temps you mentioned you shouldn't have much to worry about at all.

[Jeremiah Robinson]

Thanks for your help guys.  Good to know bacteria aren't sensitive to temp. change.

I don't have constant flow but am using an indexing valve, so I can vary the amount of time I pause before filling the next bed.  I guess that can be my temp. control.

[Vlad Jovanovic]

Naw, just run it the way you planned...you'll be fine. The bacteria are affected by temps... just that it doesn't really play out as bad as we would think (when going by the impression 'books and charts' are prone to create in us)...