Backyard Aquaponics
A place to discuss aquaponics

Thanks folks, that gives me some keywords to start reading about.

Thinking about it, it seems to be that since the system will be colonized from the local bacterial fauna they really, really should be adapted to overwinter in the local conditions in some sort of resting state...Maybe just leave the grow beds dark, flooded and stagnant, drain the pipes, let it freeze if it wants to...Surely every little pool up here doesn't have a big issue with getting started each spring? More homework.

Welcome aboard Murray. I am down the coast from you in Vancouver, Washington. We may get a bit more sun but not a whole lot. I've had plants in a solar greenhouse for the last two winters. They were in dirt rather than AP, but I did learn some things.

What I noticed is plant growth slows to almost nothing, however they were still there and I would assume using some nutrients. I had a greenhouse tomato that I actually had to cut down and remove to put the AP system in. Things like broccoli, cauliflower, etc. do fine. Because of the warmer water this winter, I'll make sure I grow the same varieties I'd grow in summer of those vegetables. The cool season ones didn't like the warmer feet this past spring as the system was getting going.

You'll want to plan ahead so plants are well established by about the 1st of November. They'll hang and grow slowly from there until about Feb 1 and then take off again. Or, at least that's my assumption based on how the dirt gardening went.

Unfortunately the bacteria need oxygen to live so they cannot remain flooded.

Welcome Murray!

You'd use more electricity trying to keep tilapia warm over the four or five months than it would be worth, if you're not able to offset the expense by growing plants too. I have tilapia in our basement, and even in a sheltered environment it is a bit dicey with the drafts and cold concrete over the Winter. I had been running 1000 watts of aquarium heaters for about 250 gallons of water. Ran with a 400W metal halide growlight for a few months growing plants in the basement but stopped doing that for electricity use reasons. FWIW I was able to keep the tilapia in the basement without plants for about nine months with no problems, just change out some of the water from time to time. Nitrates got over 300 but didn't seem to hurt the tilapia. Got some nitrite spiking due to gravel volume being only 100 gallons.

The heaters are by far the largest operating expense for my system, as it was configured using loop siphons and CHIFT PIST so it runs on just one 40 watt pump. I'd much rather have bluegill in it I think for our climate (PA), if it were looked at for electricity use alone. If you have to dump a lot of electricity in it then it kind of violates the sustainability goal.

It might be worth it to harvest tilapia before it gets too cold then run it as a pee-ponics system during the Winter if that doesn't make you squeamish!

I suspect that tilapia will not be a very viable option since you need to keep the water over 55-60 F depending on species and they don't even start getting good growth till the water temp is up over 70 F. Even in Florida, I'll have to provide some cold protection to my system for Dec/Jan.

As to ways of keeping a system alive without fish, you can easily set up a slow dosing system to supply the ammonia to keep the bacteria alive even if you don't have fish in. So long as the Set up stays warm enough not to freeze the flowing water, you can easily grow cold weather crops. On Hydroponics forums I've read plenty of stories about greenhouses in Scotland growing cabbage, kale, lettuce, etc in greenhouses over winter. Perhaps with the low photo period they may not grow quickly but then if you are running as a half shut down state, you wouldn't need to be spending your days there. With a huge mass of water and pumps and gravel beds in a large greenhouse, I suspect that you can keep things from freezing up if you say the normal low temp is -1 C (of course that is my assuming that the -1 C is the overnight low and that the daytime temps get a fair bit warmer.

Another option to consider, go into business overwintering people's fancy Koi for the cold months income stream. I know there is a place up in Michigan near where I grew up, they are a water garden nursery place that over the winter, takes care of the fancy koi from people's garden ponds. People might be willing to leave their cheap gold fish in the garden pond here over winter but if they spent lots of money on Koi, they don't want to risk them dieing over winter so they take them to the fishy kennel. (there are lots of seasonal residence near where I grew up.)
Anyway, that option would likely keep a person busy over the cold months and it would probably provide enough nutrients for the bacteria to stay functional and a small amount of plants to take up the nitrates and provide some greens for the home table over the dark months.

Or as people have said, a cooler water fish might be more appropriate though the feed for such fish is a little more questionable on the sustainability front. Perhaps you would need a really large worm farm and you could get paid to take care of the food waste from a nearby restaurant to feed the worms that could feed the fish (a hand full of worm castings are a handy thing to help start a new grow bed off right and worm castings could be an added income stream.)

+1 for shutting down the growbeds over winter, and using a large insulated biofilter.

Thanks again for more ideas and thoughtful responses!

Those of you running heaters might want to check out passive solar tech. which is getting pretty common up here....orders of magnitude more efficient than electric heat. A heating fluid (water or glycol) in a closed loop passes through (by solar electric pump) a heat collector (often vacuum insulated glass tubing) and then to a heat exchanger.

I need to do the math but I think with the thermal mass of a large tank or two in a greenhouse, I probably would have enough heat inertia to get things through the cold snaps, at least on the shoulder seasons...maybe I could keep 16 C to keep tilapia alive and warm it up into the twenties to get them growing during the summer...will check out other fish too, but can't imagine maintaining water quality for trout or char.

I still have a strong preference to shut right down in the winter. Harvest fish, maybe some bubblers could keep the culture beds aerated and not frozen, arrange some sort of low level ammonia input...? i see someone just posted about 'large insulated biofilter..

ps i love the worm farm and pee ponics ideas!

Hi Murray,

I'm in Toronto and will need to deal with similar issues. My fish of choice is channel catfish over tilapia, as long as water doesn't freeze they should be able to over winter. I'd really like to grow trout but it gets too hot here in summer, and my cool basement is rented out. I'm hoping that with greenhouse location and the amount of water the greenhouse will stay well above freezing, I need to sit down and do the design and calculations. I'll essentially feed them table scraps/worm farm/greens and avoid commercial food as much as possible. It may be that I can grow Tilapia during the warmer seasons, and use the Tilapia partly as a protein source for the catfish, and in the winter let the catfish cool down enough that they require minimal protein.

I'll be looking into solar water heaters, solar panels, automated curtains etc. Depending on how close to 65 degrees I can keep it using these methods I may consider installing a natural gas fireplace in the greenhouse, if that's an option in a fish house, failing that I may see if I can get someone to extend a line from the radiator system in the house into the greenhouse. My understanding is if the greenhouse can be designed efficiently enough to keep temps at 65 or over the bacteria will survive, is this correct? I think it's a matter of paying attention to all the details; the air coming in would need to go through underground tubes to preheat it slightly, one side of the greenhouse will be attached to a small insulated but unheated space next to the house, I will need to consult with various experts before proceeding. I really require this thing to operate on it's own in the middle of winter in a power failure, I want it to run off batteries and use the grid as backup.

I expect that the climate situation is rather different between Toronto and BC would be a bit different. However, I doubt that you have to keep the growbeds as warm as 65 F in order to keep the bacteria alive. Granted, as the temps drop the bacteria slow down but so do most types of fish and therefore it isn't such an issue, as the temps come back up, the feed increases and the bacteria gear back up to full production. I think the main thing is to keep the system from freezing. I know there are pictures of some one's system (maybe gotfish) where things really did freeze up, perhaps he will give a comment as to how ramping back up that spring went.
Anyway, there are many sub-varieties of bacteria and the local species should be able to survive cooler temps, the trick being that you need to keep the water flowing to keep the beds alive.

A note, trying to cycle a system up while the water temps are really low will be very difficult so adding a large load of new fish into a system that was shut down over the winter might not be something you want to do each spring. My guess is if the water and grow beds can be kept above freezing with a minimal load (fish or fishless) and a small crop of cold weather greens, you will have a far easier time cycling back up in the spring. I suppose the biggest questions are, can you keep the greenhouse above freezing for the winter without too much extra cost and would the cost of running the pumps for the winter outweigh the costs of set-up and shut down. There may be issues with simply draining the beds and leaving them since the solids left rotting in the beds might provide an unwanted place to harbor bad bacteria, then when re-starting there will be all that dried out sludge in the system. If temps can stay above freezing and the cost of running the pumps over winter are not too bad, leaving the system running with minimal load will probably save you 3-6 weeks on cycling back up in the spring.

Of course there are people here who have dealt with shutting down parts of systems for the winter and perhaps they can prove me wrong and tell you how they deal with it.

The amount of water in the system will assist in keeping the greenhouse at or above freezing. There is a latent heat effect in water such that it expends a great deal of heat in order to freeze. As a test last winter, we let our greenhouse go without heat during a cold spell where night time temps were getting down to about 17F and the greenhouse only got down to 35 F with the heat sink (in the form of 5 gallon buckets filled with water) we had at that time. We now have over double the volume of water with the AP system, so would expect temps to stay even higher with no added heat.

Our greenhouse was designed as a solar greenhouse and has insulated walls on the North and an insulated wall on the East that has a large double pain window in it. I know temps are colder in your areas, but the water does make a difference along with proper design for cold areas.

Also, if you can keep it up to 65F in the winter, you can grow tilapia throughout the winter. They should continue to grow at temps above 65 with the best growth at higher temps. When temps drop into the 50's (F) is where they fail.