Backyard Aquaponics
A place to discuss aquaponics

Which of the winter vegetables grow best in your system? I especially like broccoli, brussel sprouts, cauliflower, cabbage, leeks, spinach, peas, and rhubarb.

Pretty much all of the plants you've mentioned there will grow well in an aquaponic system clueless, the only one that I can see which might not be the best is rhubarb. Rhubarb is a bit slow growing, and seasonal, it's best to have plants that will grow quickly and can then be harvested to remove the nutrients from the system..

Rhubarb is also a perennial. How would that work? What about asparagus? They're supposed to last 20-30 years!

SueinWA

Hi All,

Just found this place and look forward to 'chewing your ears' about things

About rhubarb, it is also toxic (see here: http://www.rhubarbinfo.com/rhubarb-poison.html), which raises some questions for me. Do chemicals leach from the plants and show up in the return water in aquaponic systems that may impede the growth and development of the fish? I know certain marine algae species can release turpenes (e.g. Caulerpa taxifolia) into the water which has a retarding and toxic effect on the inhabitants of such systems so maybe other plants with known chemical 'issues' might be a problem too???

Another question... Short days (long nights - photoperiod is more correctly defined by the length of the night) are associated with low temperatures and growth rates of plants are related to temperature (photosynthetic rate can be increased by raising the temperature). So even though these veggies are classed as winter veggies is their growth rate fast enough during the winter to make them effective nutrient harvesters? I have been wondering about this now as I research aquaponics as I intend to move to Tasmania soon where the winters are rather wintery and I'm wondering if one may need to add additional filtration for nitrate 'digestion' (such as a big nitrate coil etc) during the colder months???

OzV,

Not knocking the nitrate coils or that they work, but as far i i understand, the need to be very fine tuned.

For those that don't know the nitrate coils are a lond run of pipe with media. due to the lond run and the very slow flow rates through them an anoxic region is created where bacteria grow that reduce the nitrate back to nitrogen gas ( i cant remember the other half of the equation )

feel free to correct me if i'm wrong about eny part, ozv

The trick is to keep the coil anoxic (not hypoxic as in no oxygen) if there is zero oxygen then you start producing H2S (rotton egg smell and quite toxic)

Too much water flow and hence oxygen just turns them into the same biological filter as your main filter.

Have you had previous experience with nitrate coils ozv? i'd be very interested in any info.

Steve

Yeah - I wasn't recommending a nitrate coil, it was just an example of a nitrate digestor that you could use. They are more associated with marine aquariums and probably not real suitable for this kind of thing. I haven't made one myself because I rely on deep sand beds in my marine aquariums to keep nitrates at or near zero. Fine tuning the nitrate coils is not that difficult providing the tubing is long enough and you provide sufficient substrate on which anaerobic bacteria can become established. You take 6mm plastic airline (or black ag tube is even better to prevent algae growing in it) and just tap it off the main return line (which is a much larger diameter) with a small adjustable valve to control the flow. I don't know how successful they would be on very large volumes of water as would be found in an aquaculture pond. I have seen them in use on both marine and freshwater aquariums where they are very successful. This is a plan for one that I drew up when I was looking at making one for my 6x2x2 marine tank (decided against it because I made a deep sand bed instead which is just as effective and way more interesting from my point of view - lots of little critters in it. It would be good if you could not get hold of really fine sand for your deep sand bed):



The blue material is something like bioballs or cermic noodles or something like volcanic rock or anything that has a high surface area (you could probably even use fine sand like a deep sand bed). The plastic tube gets wound around the central tube from the top and wound towards the bottom where it is then run into the middle of the central tube. The central tube has a cap on both the top and bottom which is water-tight. Water flows down into the plastic tube and into the central tube which then fills up with water, passing through the media as it does, and when it reaches the top it exits through the hole in the top into a sump or tank. The idea being that aerobic bacteria will line the sides of the first 3/4 of the plastic tubing and will remove the oxygen (hence the reason for the narrow tubing giving it a relatively high surface area to volume ratio) and from there onwards the anaerobic bacteria populate the remainder of the plastic tubing and the surfaces of all the media in the central tube and they metabolise nitrate into atmospheric nitrogen which then bubbles up through the media and out into the atmosphere. Would have to experiment with plastic tube length (some recommend about 100ft but I have seen reference to much longer), central tube diametre and height, flow rate, and media selection to get the best results.

I guess my real concerns are what do you do to remove nitrates/phosphates in an aquaponics system in winter when plant growth is not active or whether the growth you get from winter crops are sufficient to act as a nutrient harvester to remove nitrates? An extension of this, that I only just though of now, is what do you do between crop rotations where plant 'demand' will be significantly lower than fish 'supply'? Have a number of different plant beds at different stages being fed by the one fish pond/tank I guess???

G'day OzV,

Good to see you here..

This is the beauty of aquaponics being such a balanced system with the fish/plants/bacteria so intrinsically linked. Over winter the fish tend to slow down their feeding as the temperature drops, and as such less nutrients are available for the plants, or from the other point of view, theres less nutrients needing to be stripped from the system.

Of course this varies incredibly depending on the climate, if your in tropical areas the system will remain fairly constant year round. Here in Perth when the temperature drops over winter, the whole system slows down in unison.

Also the idea is to stagger the harvesting of grow beds so that there's a fairy constant level of plants extracting the nutrients from the system....

First up, sorry to Clueless for hijacking this thread

Thanks for that information. The staggered harvesting of beds makes sense.



This might be a problem. Because I want to relocate to Tasmania I was planning to heat the water (haven't worked out how yet - I visted a rose farm near wagga a few years back that had an excellent method of heating their rose houses (large plastic tunnel houses). He bought an oil burner and then went around the local mechanics and they gave him barrels of old sump oil which he burnt to heat water that was pumped around in metal pipes throughout the tunnel houses - burnt really cleanly and was free to fuel) because I am interested in aquaponics and trout, the main species farmed down there, don't seem to be suitable for aquaponics from what I've read so far and Tasmania won't allow other coldwater species in. So the whole system wouldn't slow down in unison because the water temperature will remain failrly constant. I'm not sure what to do. Photoperiod affects most plants so it doesn't really matter if I use tunnel houses and heat them, unless I use artificial lighting and I don't think that this option is economically viable. My long term plan is to move to Tasmania where I will teach high school science, buy property down there and gradually build up an aquaponics system so that I can phase out the teachng and gradually go to full time aquaponics. *shrugs* I need some inspiration. I got a lead today that I hadn't expected. It seems that WA fisheries is doing research into the viability of stocking black bream into inland water, including freshwater, and they are also found locally in Tasmania. Maybe that's the go. Anyone ever kept bream in freshwater b4?

Dunno why I'm a guest in that reply *shrugs* Maybe I timed out..

Anyway - here's an interesting link

http://www.fish.wa.gov.au/docs/aq/aq024/index.php?0305

ozv,

I've also got a marine tank, (and about 4 freshwater ones )

I love it, live rock and coral. but they are so much more work and expense than the fresh!

You can always give it a go and test for nitrates if they are too high if its a real concern for you. then just change out water.

Besides i'm not worried about nitrate levels below about 50 or 60PPM.

This would send a tropical (or marine) aquarists head spinning

There is WAY too much stressing by aquarists over nitrate! i keep my tropical tank at 40PPM nitrate and have water wisteria under lights (white and purple tubes) They grow so fast that i need to cull them back about every month and a half becasue they have filled 3/4 of my 4 foot tank.

At 40ppm nitrates in this tank my angels, clown loaches, brsitle nose and others are still happy over a year on.

And silver perch are MUCH hardier than the tropicals in my tank

Now you've made me paraniod........
just tested the tropical tank...........WOW read on.........

I have been lax with my water changes in the tropical tank over the last couple of months. couple that with not having the purple grow light on and the plants not having grown at all and.............My nitrates are off my testing chart which ends at 160PPM!!!!

Yet my angels have just gone though a breeding cycle.
no diseases.
no signs of stress. (ammonia and nitrite always 0PPM)

TRUST ME, don't stress over the nitrates as everyone else does!

Oh by the way. you may have to log in twice or you will be posting as a guest. its just a quirky thing. if you log in and your name doesn't appear next to the log in button then do it again.

Cheers
Steve

What does every one think i should plant in my virgin growbed?

I'll probably start with seedlings.

I have some silverbeet that is still growing in the gardden, EB, what do you think of up rooting one of these and transferring it to the new grow bed?

I just found a mid winter tomato sprouting on my doorstep. Strongly suspected roma acid free organic stock. This thing was growing in a frost. it has purple leaves and grew out of 2 mm of soil on top of concrete.

It's now inside getting TLC and will be used for seed which I will gladly share with the group as soon as I harvest some - (3-6 months I don't know if these tomatoes auto flower or need to be seasonally induced yet)

It's certainly got what it takes for off season greenhousing though.

Parley grows well in winter, oregano, brassicas are always in demand. When greenhousing if aiming for profits look at your stores now and note down what is needing to be imported or what has the price way up. Make note of the dates, variety and price.

That is one tough tomato- nothing says Im tough like the description above - sounds like the type I will need that way I could posibly get as far as a harvest one day

very excited to be starting my greenhouse on the weekend. I am convinced they are the go. Have put a sheet of thick plastic over a trough with lettuce and capsicum seeds in it, which in freezing adelaide conditions should definately not be growing, but I have germination as of day 5 in the lettuce section and day 10 I have 2 capsicums. In fact, the lettuces are gonna need thinning out, they are starting to look like lawn!! When I lifted the plastic today, the soil was warm, can't believe the difference it makes. Can't wait to let em get to 3 or 4 cms and transplant them into my grow beds in a month or so. Better get a wriggle on

monya, you are using a poly tunnel, yes?

are you going the double layer film or just the single? the double layer is supposed to have OUTSTANDING insulating properties, as a little fan keeps air forced inbetween the two skins. Some people don't realise that in many forms of insulation its actually the air that is trapped in the medium that does the insulating. thats why fiberglass batts are so "fat".

The fan used can be quite small, just like an oversized computer powersupply fan.