Raft vs. Media filled Grow Bed (Sustainability)

[James McCullough]

Lots of people seem to advocate an Ebb & Flow system for hobbyists and a raft or DWC system for larger commercial applications. So what's wrong with a large scale E&F system? Okay so the media could get expensive, solids loading may be too intense at large scales and the total ratio of fish weight to system water volume is lower.  However, in favor of Ebb & Flow is the potential for greater mineralization of solids to provide more and different kinds of nutrients (supposedly eliminating the need for nutrient supplementation), better electrical efficiency by reducing active aeration requirements to the hydroponic/nitrification side of the system along with non-continuous pumping, the elimination of clarifiers and degassers and potentially better water usage efficiency (water required to handle solids from filters/clarifiers vs. lower evaporation rates in raft system).   Has anyone tried or considered a commercial sized system that uses a 0.5 lb/gal fish to tank ratio (at max) and just increases the tank to bed volume from 1:2 to 1:3 or greater?  Seems like if you kept the plant to fish ratio the same while making such an increase in bed size then this would handle the issue of solids in a large E&F (just till thoroughly between harvests and keep up the worm population in the bed). Any thoughts? I'm trying to design a system that uses primarily solar power and collected rainwater while still being scaled to a small commercial size, so an effective E&F system would be ideal if possible.

[Eric Warwick]

The quick turn around crops like greens are especially conducive to DWC and, nce they're harvested every week,will be hard to harvest  in a media bed to make to make significant money. However, many commericial people like Green Acre Organics in Brooksville, Florida are doing a mixed system of DWC, Media, and NFT. This enusures crop variety,and the money that comes from diversity.

[Vlad Jovanovic]

James, I firmly believe that the (near) future of small commercial aquaponics should (and probably will) be geared towards an integrated or 'hyrbid' approach. Media beds (along with sane stocking densities and composting worms) are already being utilized in lieu of clarifiers, net tanks, solids settling tanks etc...to pre-filter water for DWC rafts. This just seems like the logical evolutionary path for small scale plant based operations for many reasons. Crop diversity for customers, lower maintenance, not removing nutrients from the system, and some other things that you touched on in your post are but a few reasons why.

Unfortunately, there are no proven hardcore numbers or a step by step instruction manual (ppl like that sort of thing I guess) at the moment for people to latch onto and run with, neither from a university or nor a research center who publishes their data. Instead we have a few individuals experimenting, or running analysis on various hybrid system designs based on some small 'backyard' hybrid systems 'experiment' wondering if it will scale up. Or scaling it up and having success with it after having already gained an understanding of the AP basics as well as some in's and outs of what happens in an AP system when you...and why that happens...

Up until now it seems like most folks have chosen one of two paths in the AP dichotomy. Either the 'American/UVI/Raft based system (this includes Nelson Pade, Friendly's and too many others to list), or the 'Australian/IBC Tote/Media' route. The reasons people have done this, although wholly understandable within the context of the infant/toddler stages of mainstream awareness of aquaponics, are very soon, not going to be valid as we're fast approaching 'puberty'. 

It seems obvious that media beds and rafts (depending on the operators goals of course) belong in the same system, harnessing the benefits of both. Again, it is my opinion (as well as others) that this can be done by respecting a few 'hybrid system' principles, much the same way people respect a few basic ratios and/or principles of "standard" AP  (media based, or raft based) in order for either to work well.

Your thoughts on increasing media bed volume to deal with solids is valid, (though might not be the most efficient) but if I understood your drift correctly and the direction of your thoughts, I have to say I think you would be doing yourself a dis-service by boxing yourself into thinking that one must follow, or "choose" between one school or the other.

And yes, I fully expect to catch a bit of a grilling for a newbie in such an "experimental" direction, but there, I said it 

[Vlad Jovanovic]

I meant to say... "for directing a newbie in such an experimental direction"...

[Eric Warwick]

I don't think it's all that experimental, though what I'm about to say is a theory of mine. Simply use the calculator for media beds and then plant less densely (tomato plants) in the media beds then the DWC beds. 

[Vlad Jovanovic]

It's really not all that experimental. Actually I personally don't feel that it is any more or less experimental than AP itself. But I can understand why some other folks feel differently. 

It's probably not something that someone getting into AP from a 'feel-good-happy-go-lucky-I'll-jump-right-in-and-start-a-system-and-when-a-million-things-start-to-go-wrong-I'll-pop-in-on-a-forum-and-ask-for-help, should go with, as there wont be too many people able to give help out with solid concrete answers. 

But someone wanting to go even small-commercial, should have a firm grasp of both the basics as well as some of the niche processes that go on, as it might help the success of your operation. (Well at least on the production side, actually selling what you grow for a profit is a whole 'nother mystery :)

IDK Eric...IMO half of your idea seems right. I have 8 media beds for pre-filtering, at first I only plan to plant half of them, leaving the other half able to to 'full duty' bio-filtration, and giving the system time to mature (meaning build up a store of different nutrients).

Tomatoes (cukes too) are nutrient HOGS especially with the P and K when flowering/fruiting, getting them to veg in a new AP system is probably easy enough, getting them to flower/bear fruit is where people run into problems (again, in a newish system, with 'no-additives')... not to mention they can form MASSIVE rootballs that can clog up a media bed and create anaerobic zones, so if I was to plant tomatoes I'd do it in the 'dual root-zone' way (where's the damn "copyright" symbol on this keyboard hehe) for reasons explained here...http://aquaponicscommunity.com/group/fish-less-systems/forum/topics... (yeah I know you know Eric...shameless plug :) 

But I think you are definitely onto something with the 'plant less densely' in the media bed idea though. And it's not like you're gonna pack it chock full of lettuce and such, since you have the rafts for that. Might as well use the media beds for other things your customers might like (toms, cukes, zucchini, peppers, eggplant etc...) and for plants that need more to anchor onto for support than a raft would provide. 

[Eric Warwick]

Well you do own the thread.
Vlad Jovanovic said:

 so if I was to plant tomatoes I'd do it in the 'dual root-zone' way (where's the damn "copyright" symbol on this keyboard hehe) for reasons explained here...http://aquaponicscommunity.com/group/fish-less-systems/forum/topics... (yeah I know you know Eric...shameless plug 

[Vlad Jovanovic]

That'll be $5 please...

[Carey Ma]

I think there is something to increasing the size of the media beds. However I think it is more important to be able to evenly spread out the load of solids coming into the system. Either that or use a huge bio filter/ reactor then it doesn't matter what style of hydroponics methods one uses because you already have a specific place to derive your nutrients from.

[Vlad Jovanovic]

The problem IMO with using UVI numbers is they are VERY, VERY heavy on the fish side, and therefore have much more solids to deal with than someone who is primarily concerned with plant production. 

The potential problems with auto-siphons and keeping the water moving properly could be solved with a repeat cycle timer and a low-flow indexing valve in a Flood and Drain setting. (As some beds are filling, others are draining, keeping the flow relatively constant).

Again, stocking density and worms seem to play a HUGE role in avoiding solids build-up. Using UVI's stocking densities for such a 'hybrid' system would seem like a lost cause right off the bat (unless you had media beds the size of Rhode Island). 

If the fish are you're primary concern then media beds as your main pre-filtering for DWC (and whatever else you attach, NFT, vertical elements) would be un-wise to say the least.

I would think that UVI already needs (and has) "serious aeration" as it stands based on what they've published.

Many other folks have shown you can grow tomatoes and all sorts of things in a DWC system if you are so inclined and take care to create some some support that heavy fruit bearing cultivars would need...no need to add media beds for just that side of things...

This is a foto of Chris Smith's (Coastview Aquaponics family farm) DWC tomatoes. Chris btw has been running some 'hybrid' systems for over a year now.

[Sahib Punjabi]

Hello James,

I agree wholeheartedly with Vlad in that the "future of small commercial aquaponics should (and probably will) be geared towards an integrated or 'hyrbid' approach".

Here at Sahib Aquaponics Research Farm, we have been running Hybrid Aquaponics systems since August 2010 and have been able to grow an incredible variety of vegetables and fruits (trees too), without having to waste any of our nutrients. We have actually incorporated other growing techniques (horticulture / permaculture & organic gardening), and supplement the watering of such with water from our Aquaponics systems.

James, I see Aquaponics as just one part of the food growing puzzle...to me it is the most important one and everything else is based around it. The control of fish waste, an Aquapons "gold fertilizer", is in most cases in your hands re fish stocking densities. I do not see any one system, media, raft or verticals as being superior to the other. They all have their place in a Hybrid system and it all depends upon what and how much you want to grow. In an Urban setting, in less than 2,000 sq foot "waste-land' space, I have managed to grow an incredible amount and variety of food. Each situation is going to be different and you cannot document with certainty about fish / grow bed ratios. Depending upon the type of fish/ the temperature/the amount of sunshine & light/ fish stocking densities/ feeding amounts, types of feed and times feed/ produce amount and variety grown and so on, will you be be able to discover what works for you. Further, there is adequate research already done as to what plant growth volumes one can reasonably expect in the different types of Aquaponics systems. They are extremely hard to replicate as your particular environment may not resemble that where these results were recorded.

All I can suggest is that design your system to use the most efficient pumps given that you want to use Solar, make use of gravity as much as possible and go HYBRID :-)

God bless  

[James McCullough]

So let me clarify (no pun intended) the goal of the design. I'm a senior Environmental Engineering student at Georgia Tech working with a team of students under a professor to design the system. The system will be built in downtown Atlanta on Truly Living Well's farm in MLK's old neighborhood. Their mission is to bring together the community through education and the availability of organic produce (not sure if it's certified), thus what they want  us to deliver is a "closed loop" design (not entirely because they'll be providing a consistent input of food waste from their small farm and local restaurants/farmers markets) that kids and adults from the neighborhood can come see to learn about the processes that go into the production of food. Thus, we aren't necessarily worried about going heavy on the fish or produce side so much as making a robust system that doesn't demand extra inputs except for in emergencies. As far as "commercial" it doesn't need to be a money making juggernaut, but rather stay afloat (they've already got a huge network of restaurants, markets and neighbors who are willing to pay a premium for a product they can feel good about). On the other hand, as engineers/engineering students we would love some hard numbers, but as you said I think that the relative infancy of aquaponics is responsible for the general lack of such numbers other than from the big time systems and anecdotes from experimental set ups. That's why my professor is leaning toward a UVI xerox but downsized, the numbers are there and the system is proven. Ultimately though I feel that a straight UVI copy won't be delivering quite what the folks at the farm are hoping for. We've been considering a hybrid system but to convince my prof. I need some hard numbers or sizing info from an extremely reputable source. If I can't get this, would you suggest that I try to convince him to start with a small media bed setup as a proof a concept and learning experience and then proceed to move to a hybrid setup? No matter what option we go with, we'll be recording a TON of data and I look forward to sharing the results

Vlad Jovanovic said:

James, I firmly believe that the (near) future of small commercial aquaponics should (and probably will) be geared towards an integrated or 'hyrbid' approach. Media beds (along with sane stocking densities and composting worms) are already being utilized in lieu of clarifiers, net tanks, solids settling tanks etc...to pre-filter water for DWC rafts. This just seems like the logical evolutionary path for small scale plant based operations for many reasons. Crop diversity for customers, lower maintenance, not removing nutrients from the system, and some other things that you touched on in your post are but a few reasons why.

Unfortunately, there are no proven hardcore numbers or a step by step instruction manual (ppl like that sort of thing I guess) at the moment for people to latch onto and run with, neither from a university or nor a research center who publishes their data. Instead we have a few individuals experimenting, or running analysis on various hybrid system designs based on some small 'backyard' hybrid systems 'experiment' wondering if it will scale up. Or scaling it up and having success with it after having already gained an understanding of the AP basics as well as some in's and outs of what happens in an AP system when you...and why that happens...

Up until now it seems like most folks have chosen one of two paths in the AP dichotomy. Either the 'American/UVI/Raft based system (this includes Nelson Pade, Friendly's and too many others to list), or the 'Australian/IBC Tote/Media' route. The reasons people have done this, although wholly understandable within the context of the infant/toddler stages of mainstream awareness of aquaponics, are very soon, not going to be valid as we're fast approaching 'puberty'. 

It seems obvious that media beds and rafts (depending on the operators goals of course) belong in the same system, harnessing the benefits of both. Again, it is my opinion (as well as others) that this can be done by respecting a few 'hybrid system' principles, much the same way people respect a few basic ratios and/or principles of "standard" AP  (media based, or raft based) in order for either to work well.

Your thoughts on increasing media bed volume to deal with solids is valid, (though might not be the most efficient) but if I understood your drift correctly and the direction of your thoughts, I have to say I think you would be doing yourself a dis-service by boxing yourself into thinking that one must follow, or "choose" between one school or the other.

And yes, I fully expect to catch a bit of a grilling for a newbie in such an "experimental" direction, but there, I said it 

[James McCullough]

I'm extremely interested in your particular system as we will also be implementing the system in  an urban "wasteland" type space. Do you have any data available on your hybrid system on the research farm? As you said, no two systems are going to be exactly alike, but some general sizing/loading data would really help.

Thank you
Sahib Punjabi said:

Hello James,

I agree wholeheartedly with Vlad in that the "future of small commercial aquaponics should (and probably will) be geared towards an integrated or 'hyrbid' approach".

Here at Sahib Aquaponics Research Farm, we have been running Hybrid Aquaponics systems since August 2010 and have been able to grow an incredible variety of vegetables and fruits (trees too), without having to waste any of our nutrients. We have actually incorporated other growing techniques (horticulture / permaculture & organic gardening), and supplement the watering of such with water from our Aquaponics systems.

James, I see Aquaponics as just one part of the food growing puzzle...to me it is the most important one and everything else is based around it. The control of fish waste, an Aquapons "gold fertilizer", is in most cases in your hands re fish stocking densities. I do not see any one system, media, raft or verticals as being superior to the other. They all have their place in a Hybrid system and it all depends upon what and how much you want to grow. In an Urban setting, in less than 2,000 sq foot "waste-land' space, I have managed to grow an incredible amount and variety of food. Each situation is going to be different and you cannot document with certainty about fish / grow bed ratios. Depending upon the type of fish/ the temperature/the amount of sunshine & light/ fish stocking densities/ feeding amounts, types of feed and times feed/ produce amount and variety grown and so on, will you be be able to discover what works for you. Further, there is adequate research already done as to what plant growth volumes one can reasonably expect in the different types of Aquaponics systems. They are extremely hard to replicate as your particular environment may not resemble that where these results were recorded.

All I can suggest is that design your system to use the most efficient pumps given that you want to use Solar, make use of gravity as much as possible and go HYBRID :-)

God bless