Backyard Aquaponics
A place to discuss aquaponics

8 weeks for lettuce grow out in DWC... a bloody good reason not to do DWC then...


Why would you use media grow beds in a commercial operation at all??

Of those that have adopted the "hybrid" media bed/DWC design methodology.... I've yet to see any of them post anything that even resembles good growth.... let alone greater growth/yield... than utilising other methodologies in the same footprint... (even DWC)

And why wouldn't you use/adapt proven hydroponic methodologies for such things as tomatoes and capsicums??....

Why do I get the impression of you guys, that nobody but you..........

Are you being ironic again? I miss sarcasm and irony when face to to face with people let alone via text.

The 8 week time is a conservative average. To be used to planning purposes. Obviously a lot shorter in the summer but longer in the winter. Growout time can be as short as 35 days from germination.



Two reasons I'll mention. The first is that UVI model solids removal systems are reported to produce less vegetables per kg of food input. Gb systems have been stated to produce upwards of 5 kgs of veg per kg of food fed to the fish and some recent results are suggesting as much as 10 kgs per kg food fed (scandinavian research systems). Second GB systems use less water than solid removal systems.



I thought media beds and DWC were proven hydroponic methodologies. NFT might be used almost exclusively in Australia but over seas other methods occur more frequently.

For example we have seen this one before:

http://www.youtube.com/watch?v=FHBhyqowSEc

But here is a modern Dutch version:

http://www.youtube.com/watch?v=TaIOKk-VVNM

Now I have some recent concerns over the use of GBs specifically two incidences where experienced operators have reported reduced growth after 5 years of operation. Also Ryan's report is his thread stating that he got 10kg of veg per kg of food fed to the fish in a solids removal system is exciting.

If GBs are prone to failure after about 5 years why do so many experienced operators not experience this problem?

If you can get 10kg of veg for every 1 kg of food from a solids removal system rather than the 1 to less than 4.5 kg of veg that the UVI systems report then that is fabulous. It does remove some of my incentive to use GBs but no one has come close to convincing me that is the way to go. Especially because the UVI data is so consistently less than that reported for gbs.

@ Domani I don't understand your comment.

Grow out cycles are not usually quoted as time from germination... but from seedling plant out... 4-6 weeks...

And grow out from germination in 35 days is an absolute optimum....


Got a link to those Scandinavian results Stuart?


I'm even more dubious as to this claim.... how so???

And what about the costs of plumbing water distribution/returns... from multiple grow beds... in a "commercial" design....

If the idea was sound... both cost wise and yield return wise.... why isn't it utilised in commercial hydroponics???




DWC certainly is... but media beds.... really??

And NFT is utilised all over the world.... not just in Australia....



Where is the data that suggests that grow beds produce 10kg of veg.. from 1kg of fish feed???


Few "operators" will probably have had their grow beds in operation for 5+ years....

And very few, if any... would have quantified their vegetable production....

There's a huge difference between a backyard flood & drain media grow bed aquaponics system... and a "commercial" integrated aquaculture system... or even a dinky di hobby farm...


P.S.... I haven't seen too many examples of tomatoes and capsicums... being successfully grown in DWC.... especially commercially....

Yes. Which is why you use 8 weeks as a conservative figure. 11 days from germination to first transplant plus 24 days to harvest. During winter 14 days to first transplant 70 days to harvest.



Only summary that I can publish:

http://www.nora.fo/files/13/20121024112120176.pdf




The biggest loss of water in a RAS is from the removal of the wastes (dissolved and solid) from the system. According to the UVI data one of the biggest losses of water from the system was the removal of solids from the system. In a system where solids are not removed the principal water loss is transpiration alone.



No more than NFT and in fact a lot less.



I believe someone once said that about flying.




Yeah really. Media beds were common place, they were one of the standard hydroponic techniques. NFT, DWC and other forms of media have displaced there use for some very good reasons but they are still used for some crops in some markets for equally good reasons.



I can't give you more detailed info from the Scandinavian systems other than what they have published. As to Ryan getting 10kg per kg of food you will have to ask him. The only place he has published it that I know of is in his thread.



True but those few haven't reported any problems. For example Joel, Jaymie, Faye and Jim would be the best examples off the top of my head.



Yes there is but if a technique works on a small scale (BYAP system) then it may work on a large scale (commercial) or it may not. If not why not. The number of times this discussion has come up and I still have no credible suggestions on why GB would not work on a large scale.

In the last few days I have had several reports of GBs dropping off in productivity. This is not from recorded results but the operators (two BYAP, one commercial) impression. While this is some evidence that GBs may be a bad idea it is balanced by many other systems apparently performing without problem. Also media beds were used in the early days of RAS but the size needed for them to work was demonstrated to be uneconomical. What is uneconomical for RAS may be economical for AP.



The only ones I have seen are Ryan's

I can't give contact info but a large portion were leafy greens. Originally the media was thought to be needed for their organic certification. Don't remember feeding ratios off the top of my head but they weren't anything that stood out as extremely excessive. The wind would actually cause abrasions on the plant base from contact with the media. I don't believe they did any micronutrient testing and agree deficiencies can be diagnosed and overcome but the combination of factors led to a complete redesign. I put together an extremely efficient 1acre DWC design with high density fish production, driving lanes for loading trucks, CAD layouts, 3D's, costs etc just before I left my last job but no idea what came of it. I am going to try and visit his farm in December.

I also came across this picture a month or so ago of the abu dhabi facility that shows good tomato DWC production:

http://www.dw.de/aquaponics-expert-brings-sustainability-to-the-desert/a-16808762

True enough.... but even operations that seed raise stock... do so as an entirely separate process...

Production grow out times/scheduling... are still usually based upon time from seedling plug... to harvest...

And most commercial operations probably just use seedling plugs.. rather than seed raise... which can be a significant increase on labour costs... even with auto-seeders...


I don't see where you get your yield figures from within that document...



I think that's perhaps a selective interpretation of the UVI data... perhaps from one of their many systems...

Most of the water from their solids removal processes... was reused for mineralisation processes... and nutrient supplementation... and re-introduction to the systems...


Plumbing a 12mtr long 10 channel NFT bed... and return line.... takes more than plumbing a similar grow bed area... and associated siphons/drains etc... really....




Seriously Stuart... media beds haven't been used for serious commercial hydroponics for decades...

Same goes for their use as filtration in RAS....


True enough... but they... as are most backyard systems... well until fairly recently any way....

Are based on low stocking densities/feed rates....

Those that have reported problems.... are usually operating at stocking densities/feed rates... that are exceeding their available filtration capacity....


Ok.. apart from the fact that I think the plumbing and pump/sump sizing requirements... of utilizing multiple media grow beds in a "commercial" operation is hugely costly....

There is also a concern that running commercial stocking densities/feed rates.... may well result in the need to perform regular maintenance of the grow beds... a bitch of a job in a commercially sized operation....
and one that could have serious ramifications for production schedules...

But then there's more over-riding considerations... matters of biological/environmental controls....

Both commercial aquaculture and commercial hydroponics... go to great lengths to minimise the contamination of biological in their operations.... because they pose huge problems with controls...

Why would either... or more particularly a system which incorporates both components.... want/allow the incorporation of unknown... uncontrollable biological processes...

Or are you suggesting that the biological process within a media bed are fully understood..... and/or controllable...


Both commercial aquaculture.. and commercial hydroponics... are based on decades of research.. to promote maximum profitability and return...

We define "aquaponics"... as a combination/integration.. of the two....

Why would you not just utilize the best proven design principles of both commercial industries... and just integrate them.... by linking the common denominator... the water....

Why would you re-invent the wheel.... and why would you use a methodology.. that was abandoned by both... decades ago..

Like I said the stuff I can talk about is only what is within that document. It is only one line there is no more detailed information than that in the public domain.



No idea. Havn't considered using at a GB that small in years.



Still used in some markets, for some crops today. Are they widely used today in Australia no. Are they an established method, yes.

Media beds haven't been used in RAS for decades because as I said they were not economical. The main reason for this was that they had to be relatively massive in order to cope with the waste fed into them. The cost of housing and climate control for such a big component was prohibitive. If they are considered as potential hydroponic units suddenly what was prohibitively expensive may become economical.



Yes, that is right. Relative to the size of the GB you must have a low feed rate. The low feed rate though is for the GB not the fish. For example a system incorporating a 40m3 FT running at densities of 80kg/m3 feeding 3% body mass/day connected to 960m3 of GB, that is almost 1megalitre, has the same feed rate to the GB as a 4000L tank containing 20kg/m3 of fish feeding 1% bodymass per day connected to 8000L of GB.

From the AQ side it doesn't matter how massive the media beds are as long as the waste is dealt with. From the HP side it doesn't matter how big the GBs are as long as there is enough growing area to make use of the retained nutrients. Those lightly stocked systems of Joels and others are only lightly stocked from an AQ point of view. From a plant point of view they are always chocked full of plants. From a commercial point of view too full, or over stocked, which suggests that commercial GBs may need to be even more massive than the old Tom 2:1 ratio.




Such a need would be a disaster in a commercial operation if it were not allowed for. By allowed for I mean provision made to abandon the GBs and shift to an alternative production method and alternative filtration methods. Experience tell us that this shouldn't be an issue. Now it may be anecdotal but there are a significant number of systems that haven't had a problem with bed failure after years of operation as long as they are not pushed too hard. Which will be as true for any commercial operation as it is for BYAP system.



This is a real concern and a good point. The only answers I have in response is not a very good one. On the plant side of things we don't tend to see major problems with disease orginating from the media of those operators of well run well established systems. Again Anecdotal evidence but lots of it and evidence none the less. Similarly from the fish side of things many disease outbreaks can be attributed to poor water quality rather than media beds harbouring pathogens to be released into the culture water.



Well I thought by essentially using the design published by Tom Sp, Joel and others I was using a well proven design methodology. I wouldn't be re-inventing any wheels I would be load testing old ones.

Furthermore I don't like that attitude. If everyone took that view we would never have any radical innovation. We may have innovation that refines existing technologies but that will only take the existing technology so far. Once a technology has been developed to its maximum potential a new technology must be developed. Whenever that need has arisen throughout human history people have always said "Why would you re-invent the wheel". The only exception to that is the wheel itself. Prior to that people used to say things like "Why re-invent the sled"

Further, furthermore old abandoned technologies get recycled all the time. New scientific discoveries, changed economic circumstances, changed markets and many other factors can lead to old technologies being readopted. There are a host of old technologies in the waste energy sector for example that were well developed and commercialised over 100 years ago. Today (well actually over a couple of decades over seas) they are being brought out, dusted off, re assessed and having modern scientific understanding and modern materials applied to them. All abandoned technologies that made no sense to use after the discovery and proliferation of the use of oil and gas. Today times are different and those old technologies that were uneconomical when they were abandoned have now been installed round the world and are beginning to be adopted here in Australia.

As to why. Among other reasons the use of media beds has the potential to remove many of the expensive RAS components that increase the capital cost of systems and significantly increase the total dynamic head of systems. Reducing the total dynamic head reduces the electricity demands and since the power bill is one of a RAS's major costs this can have a significant effect on the bottom line.

Stuart

In a commercial situation there is no reason to have large media beds. Biological conversion is of only incidental use to plants however it is critical for fish. There is no need for pumps to be pushing large volumes of water through media beds and I don't think (make that know) plants need it, not even need the large media beds. They are space consumptive, space wasting and heat or cool exchangers on a large scale.

I have more detailed data by McMurtry if anyone wants to see it. BTW he is not doing new research, this is a compilation to dispute ongoing debates about systems.

Stuart, Mark told me that he definitely handed off his system to Tom S. in early nineties when Boone Mora did his successful 10,000 sf system, funded by USDA. I know Mark quite well and can verify that his numbers are extremely fine tuned. Yet there can be no real debate about numbers until there is and actual controlled experiment. Well, it can be debated but it's just a lot of speculation. Also, Rakocy did participate in the Mark's early studies, I don't know about the problems he had. The real proof of Mark's system is Boone Mora's, which can be verified by him and also Tim Garrett of the USDA. If you have any specific questions, I can refer you to either of them.