Backyard Aquaponics
A place to discuss aquaponics

Arbe I know it was an example you were posing but unless the tank is one of many it is not worth considering.

You might have meant one of many tanks but for any one else reading this thread high densities are only possibly worth doing in comercial systems where the economies of scale are such that the extra expense needed to run fish at higher densities is defrayed accross multiple tons of fish production.

For backyard systems the expense would be prohibitive and just not worth the stress.

DPI figures state low stocking densities to be 30-40kg m3, and high from 80-150kg m3.... this is for Murray Cod growout in RAS.

Two local RAS farms are both successfully running around 150kg, both with native fish - cod and perch. The largest one is manned 24 hours a day, and they are just about to expand and build the largest shed built in this area... which is darn impressive when you see some of the massive packing and fruit processing sheds around here!

I dont think that the question is whether high density commercial AP can be done, but the best way to do it... ... as long as your running by similar parameters, like oxygen injection etc, the main difference is filtration after all...

I haven't seen much on the sustainability side with respect to high density.

In my case, Howling Moose Gardens, I'm based in a very cold area: Minneapolis, Minnesota, US.
It regularly gets to -20ºF (-28ºC) and can get to -40ºF (-40ºC as well) in the winter, with only 8 hours of sunlight (I'm at 44ºN Latitude).

Minneapolis and the surrounding area is also huge on locally grown, sustainable foods. In a radius of about 200 miles (320km) is the highest density of small organic farms in the US. The market is huge, but comes to a screeching halt in winter.

So my schtick is all about providing fresh, local food through the winter. I need to balance maximum plant growth with minimum energy usage.

As I also want to do this deep in the city (here I'm getting into food deserts and social justice issues) I can't afford to have huge expanses or acres of ponds or warehouses.

Given those conditions, it seems to me that a low density fish stocking is the wisest way to go, and maxing out on plant growing space. I'm starting with mostly a raft system, with some gravel-filled growbeds at the beginning of the circuit to act as solids filters. All this in an ultra-efficient greenhouse.

For me, adding high density fish would push the limits of my energy usage, and carbon footprint.

Maybe my logic is faulty...

Remembering that it all depends but...

Your carbon foot print is going to be less because you are producing more kg of produce / kW of embodied energy and more per operating kW . This is espeacially the case if you need to heat or cool because the price of climate control dosnt change with density.

As to space you need a space measured in 1000's of square meters. In the industrial parts of a town that won't be hard to do. One of the other projects that I disscused with a potential partner was re cladding a derelict factory with polycarbonate. Would gave been a cool project but never managed to find the financing. Another possibility is roof top systems as long as you can find a building with the structural strength to support the weight of water and media. I've spent many hours looking at hospital rooves wondering how to install a system on them.

Murray Cod certainly benefit from high stocking densities... to reduce cannbalism, territorial behaviour.... but losses can still be high (20%+)... and disease issues prevalent...





I'm assuming the Cod operation is Thurla Farms, based at Red Cliffs, near Mildura.... I thought they had basically wound down after 4-5 years of research.... and were operating primarily as a hatchery, not a grow out

Who's the other operation??



True enough regarding filtration and oxygenation... but commercialisation requires a return... and without a market, there isn't a return....

And to make RAS profitable, and run high densities... you're probably looking at 50 tonne per annum minimum.... and that's about the current total yearly production in Victoria....

And as noted above... requires lots of startup money... and 24 hour monitoring....

And that's just for the fish...

Nearly forgot the bigest sustainability benefit and the one that got me into ap in the first place, water use. Same amount of water more fish.


On reflection that's not such a big deal since it is only a one off expense.

But you'll lose more water with solids removal devices and external bio-filtration... through backwashing, cleaning etc...

Might not be huge amounts....

For a RAS system certainly but for AP? I was under the impression that it was the commonly held view that gravel beds were an exceptable filtration method as long as they were sized apropriately (in this forum certainly not on others). Also that the apropriate gravel bed size was dependent on kg of fish and independent of m3 of ft. or water. This being the reason why we advise that a 1:1 ratio of ft:gb is fine as long as the tank is stocked to only 50% capacity. Logically the reverse would be true that if you double the density you double the GB size.

If the Seperano's can run fish at 60 to 70 kg/m3 at only a 1:2 ft:gb ratio why cant we. Oxygen is a separate disscusion because we are talking about filtration capacity. Differences in diet my be a factor but could work in our favour in many instances. For example many of the fish we stock would have higher concentration of protein in their diet than tilapia do which could mean that species such as trout would produce less solids. However it is likely that they would produce more nutrients given the higher protein content of their food meaning that even if less GBs were required for filtration it is posible that more may be required for planting area.

Solids can be used to farm worms. So worms, casting, juice etc can be another income source(maybe marketed that the casting come from fish poo). The extra worms can be feed back to the fish.

Gees how many growbeds would you need for 10 tonne of fish

A lot, but its all relative, its just scale.

If AP is as good as we say then in time there will be ap farms much bigger than this.

In the hydro industry entry level is now being touted at a minimum of a 4000m2 gh. In ras its around 50t although that is doubtful given the results from a few operations around the place. Theoretically ap should be able to do more with less but the economies of ap systems are theoretical at this stage.

IMO Aquaponics is a compromise between Aquaculture and Hydroponics, great for backyards but not so for commercial?
For a given volume of water can Aquaponics produce as many fish as a RAS system or as many vegies as a Hydroponics system?
I think running an Aquaculture system side by side with a Hydroponics systems would yield the best results, with waste water from the Aquaculture system being used with supplementary nutrients for the hyroponics system?

Yes, Thurla Farms was the big one... definitely havent wound down... They have their own growout system and are expanding in a big way apparently.

I dont feel its required for us to name the other person that I referred to as he is a fairly private guy and we respect that - and him... so enough said.

We have export agents that are ready and waiting before weve even discussed volumes - or even WHAT we are planning to grow!
Demand is very strong if you have volume - which is currently Australias main problem with regard to fresh water fish... and one thing I love about this industry is that there is no need to be competitive... as the more everyone works together... the stronger our markets will become.

We are also hoping that in future, once there are a few more players with commercial AP... there will be more pressure available to put on the relevant authorities regarding AP becoming an Organic growing system.

Regarding start-up money and 24 hour monitoring and a few other comments that have been made... If anyone is seriously looking at starting a commercial system,then I think these are pretty obvious initial considerations... just like anything else is considered in business.

I know that many have tried and failed - and Im sure many more will... but I also know that we personally are going to do our best not to be one, and Im sure Stuart wont either

Now... your talking about requiring 50 tonne annually to make RAS profitable... but what about AP?

If you have the space for GBs... meaning you dont require solids removal... or any other paraphenalia needed in RAS, and all of the associated start-up, running or maintenance costs... why would you need that high a volume to be profitable?

Your still only talking tanks, gravel filter beds, and DWC beds... Just like Backyard AP. Your also still only requiring air and water pumps (or if at big densities oxygen generators but thats still only 1 big component add-on) but it becomes a much more simplified system component wise... it really comes down to management - and from our point of view... looking at what Stuart has had to say... they have a big advantage already having an RAS experienced guy, as well as an APer... good luck to you guys

So your pretty much talking about what Tailor Made Fish Farms has been doing... taking 10% of their waste water and adding Hydroponic nutrient to bump up the water?

I think its just the fact that AP as the symbiosis - instead of just the sum of the parts - is where the system really comes into its own though.

Once the system has been running for a while it will out-perform Hydro for plant growth rates... and the bacteria in the system makes healthier, more disease free fish due to their immune system developing naturally instead of being in a sterile environment like Aquaculture... besides, one of the best things about AP is the fact that you just feed the fish... no need to stuff around with hydroponic nutrient additions that mean the water cannot be returned to the system

Because they used Tilapia.... a low oxygen demand fish.... whereas to run that density with our native fish you'd need significant additional oxygenation.... over & above passive aeration from the grow beds....

And you're talking running that density... with a 1:1 ratio....

Effectively halving the filtration... while doubling the density....