Backyard Aquaponics
A place to discuss aquaponics

And there's the "nub" of the question...

If you adopt a higher density aquaculture, solids removal with an integrated waste effluent treatment approach....

Given the profit margin of the fish alone... what sort of scale of operation is required to balance profit viability from produce returns...

And given the approach above.. to date... has often utlised nutrient additions back into the system...

Is there a scale at which lower density media "hybrid" systems become commercially viable.... particularly in terms of fixed costs and managability/labor costs...

Personally... from a backyard perspective... the amount of fish required to provide nutrient supply for plant growth.... is grossly overstated....

And I'm wondering if the "mineralisation" benefits of a "media" component (with worms).... might actually significantly alter the balance of fish/nutrient supply in comparison to systems that have removed most/all solids...

Like I said, I can not see media "hybrid or otherwise" systems becoming viable on todays competitive platform. Way too much risk involved. While there is lots of talk about "balanced systems" or "harmonious set ups" with "thriving ecosystems" etc, contrary to their beliefs the more organnisms you add to a system the more points of failure there are and the more comprimises need to be made.

Sure there is a benefit of the mineralised solids but there is also a large negative which in my opinion outways the positive. I doubt there is a fundamental need to mineralise the solids inline. If so, why not mineralise them somewhere else?

A valid point.... but there's both an equipment and a labor overhead associated with maintenance of solids removal and mineralisation... and subsequent re-input of nutrient/mineral supplementation...

Right but marginal. What are the accociated cost of solids management inline?

Well that's going to be dependant on the level of stocking density, feed rate.... and volume of grow beds...

And that's a question that's been debated for a loooong time...

The real, and IMO.... undefined question... is what stocking density is actually required in "media" systems... to provide the necessary plant nutrient requirements....

I suspect it's actually a lot less than has, to date.... been "nominated"...

I have no doubt it is a great deal less to supply nutrient for the plants. As I have said before, why would someone provide all the plumbing and services to support fish growth and only grow them at aquarium rates at a cost to the business when orgainic fertilizers are available for a great deal less. Or is it people are facinated with the "idea" of growing some fish and veg together and not really interested in commercial volumes?

Perhaps that perspective is somewhat "tinted" by your aquaculture glasses....

Given your statement that the returns from fish can be "marginable".... then perhaps viewing an operation from a lower density, plant production perspective... might be a different "vision"

As to "organic fertilisers" being available for a "great deal less"... then I'm not convinced that, with increasing prices for both hydroponic nutrient and agrifertilisers... that's necessarily true... or likely to be so... in the future...

And then you have to deal with the disposal and possible environmental issues that might arise....

It's probably because I've been drinking the koolaid for too long, but I'm not sure I can agree with this statement. Is this saying that monoculture is best for a commercial setup because then the human beings can more easily monitor, measure, and control all parameters?

How do you feel about integrated rice, duckweed, fish, and ducks polyculture - is that too many organisms?

No, unfortunately I can not see it in Australia.

I hear you Dave, integrate to your hearts content. When doing this, you have to acknowledge any ecosystem can only support X amount of life. Trying to accommodate for each of those life forms requires a substantial amount of compromise as seen just with three majors in aquaponics (fish, plants and bacteria). With each compromise, comes a risk to each organism or to all of them.

Community gardens and small scale urban developments, there is scope for flexing the ecosystems symbiotic synergies. Can this be translated to commercial scale, feed the world type of situation? Not sure. Has anyone done it and produced large volumes of food?

I can only work with what I can measure at a commercial level and I suppose that is why I favour controlled systems. This is not to say, that is all I do as I have built some very interesting integrated gardens but at a commercial level most want to know how much can I produce in this space and if you are not getting the maximum, questions of viability come to the fore.

I think this really depends on the system, sometimes it's true and sometimes it's not. Having more organisms doesn't necessarily add more points of failure sometimes it just adds diversity.

Perhaps, but I think the point Earthan is making, is that each organism and biological process... has an oxygen overhead... and many of the inter-relationships may have over-heads and inter-actions that aren't perhaps obvious and apparent...

The more inputs, the more potential for unforeseen, or mis-understood consequences... and the harder it is to identify the actual cause of the problem... and how to address it....

Earthan comes from an aquaculture background, where profitability is often directly dependant on control of environmental factors... or at least minimalisation, if not elimination, of possible detremental external factors...

The first risk that comes to mind is very well understood and very obvious. The introduction of heterotrophs to the system due to high organic loads. I have seen these little lovelies get out of control and kill everything in the system. This is a very real risk with media beds loaded with solids.



I suppose most, if not all intensive commercial food production is well controlled. For example I am involved with the largest glass house system (32 hectares under glass roof 1st of three) being built in the southern hemisphere and it is entirely controlled from the air to the water and for very good reason, most of it from my iphone surprisingly.

From what I have learned on this project is control over all processes helps guarantee returns. When you consider the starting capital of this project is 150million I am certain the investors do not want to leave the production cycles to err. guess work. These guys operate on a completely different level.

So lets say you remove a fraction of the solid waste, say 95%. The media beds will still need a certain amount of oxygen to support the processing of the remaining waste.

Say we reduce withdrawal to 90%. This would mean that the media beds now require double the amount of oxygen that they did before?

Say we don't remove any waste we then need to ensure that the media beds are receiving 20 times the oxygen that the first configuration was receiving to ensure that the waste processing is done aerobically. This is just a mater of scale. If a system can be designed to deal with a fraction of the waste a ststem can be designed to deal with all the waste. However, you cant skimp on that scale.

Systems whether they be ras, uvi, byap ultimately have there waste processing components sized to deal with a certain total feed rate. Whether this is spread over a lot of fish growing slowly in many large tanks or a few fish growing quickly in a small number of tanks is going to matter but not as much a the scale and corresponding ability of the waste processing components to process the resultant waste.

I don't see it Stuart. How many kg of oxygen did the first scenario require per day?



I get the gist the the waste processing in any system is designed around the feed rate. That is true. How does that reflect in gravel filled beds? Are you suggesting you just have more gravel beds to deal with the solids wastes?

While that sounds like the answer, I have serious doubts. What will you do when you reach the oxygen limit of the system? Add more oxygen as suggested in the scenarios you provided above?