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So I just finished reading Sylvia's AG book, and I do not see this question addressed anywhere.

The book says the bacteria want 77-86 degrees optimally, yet I live in the NE and do not want, if possible, to have a big electric bill keeping water that warm so was planning fish that tolerate cooler temperatures (koi or perch or something, probably Koi though since I think my wife plans to let our daughter name them, cant eat something you name).


So what is a good water temperature for those in cooler climates?  I plan to start with a small system to get the hang of it and since it is November coming up, an indoor system till I determine I can do this and get the bug and want a greenhouse for year round larger outdoor systems.  I don't have to be frugal, just hate wasting money where its not necessary.

If I let the water temp hit 64 the book says 50% growth reduction in the bacteria, but is that ok?

Also, do plants in general care what the water temperature is in the grow beds? Or the wurms?

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Match your temperature levels to the needs of whatever fish your are raising. And then grow plants that like that temperature too. Yes, plants do require certain temperatures. I'm sure worms have a preference, they get sluggish when they are cold, but ultimately it shouldn't matter too much.

More worried that the bacteria production will fall off too much with cold water fish

It seems sort of obvious.  If you have half the bacterial activity you need either twice as much biofilter area or half as much food going into the system (which normally means half as many fish).

Cycling will take significantly longer, but once the bacteria populations are resilient you should be ok. It will take longer for the system to mature. Cold means you will have to be patient.


50% bacteria die-off translates to 50% less waste management, which translates to either 50% fewer fish and 50% fewer plants.  Remember, however, that as the temp. continues downward 32, bacteria drops off dramatically.  Endospores will persist until spring when the temp. begins to rise again, and the system will cycle again, but if the system gets much below 45 waste management will come to pretty much a stand still.

So, the fish you choose needs to be one that not only tolerates colder temps but also deteriorating water quality.  I strongly suggest catfish, since they are durable and have backup oxygen supply equipment.  As water quality takes a dive, catfish are able to survive and hold their own while other species just lay down and die.  The only other fish that would suit is goldfish, but that's only because they are designed to live in polluted water.

Plants will continue to grow in lower temps, but they will not set any records.  Most will not germinate at much lower than 55, and fungus is a problem.  Best bet are those greens that like cold weather - lettuce, spinach, etc.

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