my garden design... could use some input and criticism

[rob mackin]

ok i think ive done enough research. now im putting my plan on paper. so far what i have is a 24x60ft greenhouse with 14- 4x8x1 ft growbeds for flood and drain system. using murray hallams formula of 1to1 media to tank water im coming up short with respect to my media being only half the volume of my tank. my tank is essentially a canal that flows around the interior perimeter of the greenhouse. as drawn i have aprox 12500 litres of grow media to aprox 26000 litres of water. my thoughts to remedy this is to have sand and gravel cover about 4 inches of the bottom of the canal system and install some aquatic plants and use some rafts for seedlings and such. also i would like to stock around 1000 trout fingerlings for starters rather than max out stocking capacity right away. im also going to introduce some freshwater shrimp and crayfish from the lake 5 min from my home. 

im questioning my train of thought being the sand and gravel on the tank bottom counting as filter media compensating for my lack of growbed media for this purpose. also does anyone know if i could expect rainbow trout to reproduce in this enviroment as that would be so cool...am i on the right track or am i setting myself up for failure? i feel good about it just could use reassurance as this is looking like a 20k plus investment.

im also going to install a rocket mass heater designed to heat the room and the water for the extreme cold weather we get here. i would like to successfully grow year round and if that can be done in my region it can likely be done anywhere. temperatures here vary between 30+ deg c  in summer months to below -30 deg c in winter. as far as i know there is no such gardening attempt in this extreme. also be cool to be the first extreme weather success.

thanks ya'll

[Jonathan Kadish NYC AA Chair]

Sounds like a really cool project, a little insane, but cool none the less. A couple of things to consider, as your stocking density will be the least of your worries at this point. Have you considered what the effect of the earth freezing around your greenhouse would do to the temperature of your perimeter canal. It takes 2.2 BTU to heat 1 liter of water 1 degree Fahrenheit, how many BTUs you will need to keep your water at a temperature where plants will grow (20c or higher)? Have you considered that 14 grow beds will loose heat faster than a couple of large grow beds? Have you considered that the angle of the sun will not supply enough light for things to grow in the dead of winter which means 10-15kw of artificial light for 12hrs a day? Is there anyone in your area that grows year round in the soil using greenhouses or are there hydroponics greenhouses near you?

I ask all these questions because I am working on a similar project that is around 41 degrees above the equator so I have been thinking about all these issues too, but you are at 53 degrees! Find some greenhouses around you and talk to the people about what it takes to grow year round, or just pack it up and move south!

[TCLynx]

I would recommend against sand/gravel in the bottom of the fish tank if you are worried about not having enough filtration and I don't think rafts on the water will really help there either.  If you stock a very small amount of fish (stock to the filtration rather than the fish tank, you may still be ok with such a system as long as you can turn over the water fast enough through the beds you have.  Otherwise you need to add extra solids and bio-filtration.  Also since the fish of choice is trout you probably need a fair bit of extra filtration to keep up with the load while temperatures are cool.  And with the reduced plant space you may be hard pressed to use up the excess nutrients if it is too cool for the plants to be thriving.

I kinda like the raceway idea around the greenhouse but you are going to be greatly limiting yourself as well if it means you can't get up to even the 1:1 ratio.  I personally like twice as much plant bed as fish tank.

[rob mackin]

thanks guys. i'll make some adjustments to this.(larger beds and smaller water body) and i agree my temp challenges are of greatest concern. i will install a frost wall (rigid insulation buried around perimiter to 2' depth) and my raceway is actually going to be a few feet from the walls and my beds straddle it so its not that i dont have room to expand. i had laid out the room in a manner that gives quite a bit of room to move and work. i think i will just reduce the depth of my canal and figure out a better layout to acomodate for larger growing area.shouldnt be a problem. as far as the heating system goes i will install the rocket mass heater that will hopefully be sufficient. if not i can compensate with electric heat when needed. as far as lighting goes i think installing 6 or 8 1000 wat hid grow lights should substitute for lack of sun when needed. these lights also throw a lot of heat. 

thanks. good points

is trout a bad choice? because im open to suggestions. id like to grow tilapia but worry about their temp tolerance. i may try grow them as i will have to be diligent in maintaining a warm climate for my crops to flourish anyways. im confident i will come up with adequate solutions for the problems i will most definitely have...

also i will not move as this is an issue of local food production and it is important that we find ways to do this everywhere. in saskathewan we only produce 10% of our produce and the rest is imported. and we are HUGE farming province go figure. the potential of aquaponics in my mind is huge and becoming very necesary. i'm hooked on the idea and am willing to accept the risks involved. 

if i may touch on the potential benefits to installing a rocket mass heater in a greenhouse. this is an extremely efficient wood burning stove that emits co2 once its warmed up which as we know is very beneficial for your crops. if you operate in a cold climate its definitely worth some attention. so if youre not familiar with its workings check it out at permies.com

thanks again

[Jonathan Kadish NYC AA Chair]

Trout is a pretty good choice but you will need to make sure to keep water temps from spiking the summer, people are also doing yellow perch. Brown trout can tolerate somewhat higher temps than Rainbow Trout and are the option that I am choosing to try. Optimum growth for Tilapia occurs above 27c (death can occur below 17c) and that would be too expensive and nerve racking to maintain year around, but trout grow well to 20c (brown trout to 22c). The challenge for you and I is maintaining our water temp between 19-21c which is where the trout are happy and the plants are happy.

I too am doing some mad scientist work around rocket mass and double barrel wood stoves with water heaters built in to the design. I'm leaning toward the double barrel because you can put a load of wood in and have it last for 12hrs. In the top barrel I will design a heat exchanger to extract the heat in the exhaust and with all that water in our greenhouses we have a lot of mass to heat that will benefit our living organisms directly. Heating the earth seems to me that it will be less efficient.

If your really as nuts as you sound you should come down to Florida for the Aquatic Eco-Systems & Green Sky Growers Institute of Sustainable Farming: Aquaponic Technology and Design Workshop next week with Dr. Rakocy and Dr Lennard. I'll be there asking a lot of questions.

[Ernest Fields]

Can you block the peirmenter into 2 sections about equal. This would then match your available grow-bed. You would have a problem with your bacteria, as they would die at the fish water temperature.

[TCLynx]

The bacteria don't die at the fish water temperature, if they did, no one would ever be able to grow trout.  The bacteria just slow way down at trout temperatures so you need more bio-filtration to keep up.

[rob mackin]

to touch on rocket mass heaters. my thoughts on the exhaust system running underground rather than in the water are just to prevent catastrophic failure of leakage of water into the exhaust piping. as for heating the water i would simply add another barrel on top of the gasification chamber barrel which can be used to heat water that can be then routed through tubing into the water body effectively heating both the ground and the water. also the combustion chamber in these heaters is a top feed so stocking it with longer material leaving it to self feed will help keep the fire burning longer but the fact is by capturing all that heat one should only need to burn enough to heat the system and it will radiate from the floor and water so one shouldnt have to burn for 12 hrs but rather a couple hours when needed. 

if it works well enough i would certainly prefer to grow blue tilapia as they seem to be the way to grow

do i really sound nuts?

Jonathan Kadish said:

Trout is a pretty good choice but you will need to make sure to keep water temps from spiking the summer, people are also doing yellow perch. Brown trout can tolerate somewhat higher temps than Rainbow Trout and are the option that I am choosing to try. Optimum growth for Tilapia occurs above 27c (death can occur below 17c) and that would be too expensive and nerve racking to maintain year around, but trout grow well to 20c (brown trout to 22c). The challenge for you and I is maintaining our water temp between 19-21c which is where the trout are happy and the plants are happy.

I too am doing some mad scientist work around rocket mass and double barrel wood stoves with water heaters built in to the design. I'm leaning toward the double barrel because you can put a load of wood in and have it last for 12hrs. In the top barrel I will design a heat exchanger to extract the heat in the exhaust and with all that water in our greenhouses we have a lot of mass to heat that will benefit our living organisms directly. Heating the earth seems to me that it will be less efficient.

If your really as nuts as you sound you should come down to Florida for the Aquatic Eco-Systems & Green Sky Growers Institute of Sustainable Farming: Aquaponic Technology and Design Workshop next week with Dr. Rakocy and Dr Lennard. I'll be there asking a lot of questions.

[rob mackin]

i think ill change my layout to 3 or 4 grow beds 4' wide running the length of the greenhouse and reduce the water body to an acceptable ratio. also if i come to a point where im confident my system will support tilapia i would prefer to grow the most tolerant of that species if i can find some.

TCLynx said:

The bacteria don't die at the fish water temperature, if they did, no one would ever be able to grow trout.  The bacteria just slow way down at trout temperatures so you need more bio-filtration to keep up.

[TCLynx]

Well in a cold climate, you are better off heating the air some and the thermal mass rather than just the water anyway (since if you are just heating the water, you will have much more evaporation and then condensation and freezing of that water on the inside of the greenhouse which would then block more light etc.  And since the trout don't necessarily want warm water but your veggies will want warmer air, this works well.

If you go for tilapia in a cold climate, you will have far more trouble keeping the water warm enough without major evaporation and condensation problems.

I actually like catfish far better than tilapia and the catfish can still eat and grow below 70 F while the tilapia tend to stall out below that temperature.  The only real benefit with tilapia that I can really see for most people is that it would be possible to breed your own stock without needing huge ponds to do it.  But you might be able to do as well with bluegill as you can with tilapia.  Just my opinion having grown all three in a hot climate.

[Jonathan Kadish NYC AA Chair]

TC in my travels speaking to some experts I have been told that it is all about the root zone temperature and many plants will do well with cooler air and warmer roots. I think that if you reduce the surface area of water to air by using rafts in DWC and maybe even covering your fish tanks that you will mitigate some of the evaporation issues.

TCLynx said:

Well in a cold climate, you are better off heating the air some and the thermal mass rather than just the water anyway (since if you are just heating the water, you will have much more evaporation and then condensation and freezing of that water on the inside of the greenhouse which would then block more light etc.  And since the trout don't necessarily want warm water but your veggies will want warmer air, this works well.

If you go for tilapia in a cold climate, you will have far more trouble keeping the water warm enough without major evaporation and condensation problems.

I actually like catfish far better than tilapia and the catfish can still eat and grow below 70 F while the tilapia tend to stall out below that temperature.  The only real benefit with tilapia that I can really see for most people is that it would be possible to breed your own stock without needing huge ponds to do it.  But you might be able to do as well with bluegill as you can with tilapia.  Just my opinion having grown all three in a hot climate.

[TCLynx]

Well I suppose it depends on the season and plants in question as well as the relative temperatures and humidity.

Most warm weather crops need warm soil temperatures to germinate and some cool weather crops will even germinate better with worm root zone and something like 70-80 F root zone water temperature might make for better plant growth while the air temperature is in the 60-70 F range.

However, I fear if you are dealing with -30 F outdoor temperatures and air temperatures in the 30-40 F range inside the greenhouse and you are running 70 F water in the fish tank and trying to use the fish tank water as your primary heating to the greenhouse, that even with tank covers and raft beds, there will still be too much evaporation and freezing condensation issues inside the greenhouse while the air temperatures inside the greenhouse will still be too cold for warm weather crops and the water temperatures may not be all that good for the cold weather crops that would be ok with 40 F air temperatures.

So I'm kinda recommending a happy medium or a combination of heating methods instead of relying just on heating the water.  Which I expect rocket mass heaters in a greenhouse heating the floors will provide some radiant heat to the interior of the greenhouse and the air which will help mitigate over just concentrating on heating the water.  Insulating covers for the outside of the greenhouse for night time would probably also be a good idea.