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ratio between number of fish and food ratio in a start up aquaponics.

Hello, My name is Gabriela, this is my first post. I am designing a commercial scale aquaponic system in Argentina.

I know that the fish feed ratio is an important key to maintain a well balanced system. Based in Rakocy ratio (60 to 100gr/m2/day) of fish food.

Hypothetically, if I have 110m2 planting troughs I would need 6600gr per day, and here comes the question, how many and what size of fish (having 4 fish tank design) do I need to eat this amount of food, to have the proper nutrients for that m2 planting troughs in start up stage.

I ask this because despite the different ways of analyzing it, I always end up in the same crossroad.

Thank you very much!
Have a wonderful day!

Gabriela

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Hi Gabriela,

Small fry or fingerlings will optimally eat close to two percent of their body weight. Larger fish will eat closer to one percent of their own body weight in food per day.

Kilo per kilo...a one kilogram mass of small fish will produce significantly more ammonia then one kilogram of larger fish. In part because the protein content of the small fingerling/fry feed is higher (typically 42% to 46% protein as opposed to 32%, 28% or 24% protein content for juvenile or adult fish).

So the number of fish will somewhat be dependent on their size. (a 100 gram fish will eat nearly 2 grams per day; a 1 kilogram fish will eat about 10 grams of feed per day...So, ten 100 gram fish [one kilogram fish mass] will eat around 20 grams of feed per day together). Make sense?

Keep in mind those feed ratios are based not on nitrate production (using those ratios you'll have too many nitrates and will need to partially de-nitrify your water and remove solids...just like all UVI type systems need to), but on things like the proper amount of potassium, magnesium, phosphorous available to the plants.

The UVI model is wonderful for a very fish focused scenario. In some situations though such a focus on fish may not be practical, or desirable. Due to monetary reasons (equipment costs, labor costs, the cost of licencing to be able to sell and process fish for human consumption etc)...I've taken a different approach than the UVI model. 

It's not "better", or "worse"...just different since my focus is more on plant production than fish production.

 http://stores.atriaaquagardens.com/blog/

I agree with Vlad and would go with a Hybrid system where you have media beds keeping all of the nutrients in the system with a feed rate 10-20 grams/m2 of plants.  Rackocy developed his system as a way to deal with fish waste from an Aquaculture system, the plants were a bonus which he later figured out that there is more profit in the plants than the fish. The UVI system is fish centric.

Hello  Vlad and Jonathan, 

Thanks for your reply. It was interested because we are looking for that, vegetables more than fish. Of course as the fish is part of the eco-system it is important to make it work efficiently as well. We understood the feed ratio issue perfectly and we thank u both for that.

We are thinking 

. 1400m2 of land for the entire system initially, 4mts x 12mts (closed area) for 4 fish tanks (we have to find out the capacity of each tank yet), 2 x "V cone" clarifiers (we want to be able to drain the sediments), 2 net filters, 4 mts x 12 mts greenhouse for nursery bed, preliminary stage before the growing troughs, 15 growing troughs connected in a greenhouse, 1 solar pump to redirect the water from the troughs back to the fish tanks. This is the complete system but our idea is to start with the 25% of it.

Besides the feed ratio and the strategy that you use to run the system, if you wanna focus the scenario in the vegetables what modification of the UVI system design (for example in tanks, clarifiers, net filters) do you recommend?

Have a nice day! and thanks for sharing your experiences, we appreciate that so much!

Gabriela and Matias

Green Acres Aquaponics in Florida has just such a system, here is the schematic that I found on line... They are good people and offer courses on this system that I would recommend.

It might be good to ask Gina, or someone from Green Acres AP if they still have to use those degas tanks, solids settling tanks, and fines filter, even after they converted their UVI/Friendlies style system to a hybrid one. Or if some of those are just leftovers from before the conversion. I suppose it would depend on stocking densities and some SOP's.

I know that Rob Nash uses only what he calls a "polisher" between his media beds and DWC (it's a bucket with bird netting in it).

I've gotten away without any additional filtration, but designed in space to "plug in" a fines filter, or a swirl filter if need be. And I suppose I certainly do some things differently than most folks. Growing large fruiting cultivars "Dual Rootzone style" certainly helps keep the beds less clogged up 

http://community.theaquaponicsource.com/forum/topics/dual-root-zone...

(that link goes to page 4 of that thread...if anything is unclear you might want to start from page one...if your bored enough to read all of it :)

Not having all that dead root mass probably allows the worms to work on other things(like solid fish effluent)...and from a mechanical standpoint your less likely to develop large anaerobic zones if your grow beds are devoid of large dead root balls (which tend to get clogged up with effluent, then get stinky). So less maintenance there.

Certain bacterial inoculants certainly can help with remineralization/solubilization of solids, smart salting, foliar feeding, amending with worm casting tea if need be...There are many different things that you can do with a hybrid system that's more plant focused than fish centric.

The 'problem' you might run into is the lack of published hardcore data on such systems. But if GA is offering training/courses/info on their model...that would be a good place to start.

At it's core, I would recommend sticking to a ratio of 30% or 35% grow bed (surface area) to 70% or 65% DWC raft (surface area), and if you can, use grow beds that are deeper than the "standard" 30cm. And plan on about 1 to 1.5 kilos of fish mass per square meter of grow space.

Vlad do you think 250 feet of continuous DWC is too long? Might nutrients be lacking toward the end?

IDK..My DWC's are only about 144 feet long total (about 36 feet each) and I wasn't ever able to see any difference in NO3 or plant growth from the beginning of the first trough to the end of the fourth trough.

I imagine that at some point, at some length, you might have that issue crop up? I suppose it might depend on flow through rates and the amount of nutrients in solution.

I did end up "T"-ing off another line from one of my sets of 4 media beds (I have 8) directly to the 3rd DWC trough, but it wasn't because of any nutrient related issues. I just wanted to be able to by-pass my nursery trough 50% of the time so that I would have greater freedom experimenting with timing sequences (everything coming out of the media beds used to go through the nursery trough before going to the first DWC, now only half of it does).

I was more concerned with the O2 situation at the end off that 144 foot run, rather than nutrient issues. I imagine as with most things...there is a threshold beyond which problems start to crop up...Where those thresholds lie are usually dependent on certain factors...Why? are you thinking of building such a DWC?

I just gave a talk at a wall street incubator about AP and there are people just beginning to get interested in NYC. I like to keep abreast of what people are doing and being successful at. I studied with Nelson & Pade and then with Rakocy and Lennard so I have their perspective but I like to see how people are doing things in the real world out of the classroom. There are many challenges in NYC to start an operation, but I haven't said no... I just need the right partners.

Hello Guys! 

Now this is interesting, at least for us!!! (Jonathan, we are in the same situation but a little bit further south, there's no aquaponic culture here, there's no commercial scale aquaponic at all. We contacted one guy that studied in the UVI and he is more interested in the fish than in aquaponics, we felt he was not interested to help or give any advise, so we are home alone!). It takes time to spread the importance of growing organic and healthy food (this country is undeveloped in so many aspects).

We've been doing some research and studying the hybrid system that you proposed. We found that this type of system is pretty new and there's no big commercial scale with enough experience to know what could happen mixing both wonderful resources in the long term.

We have some questions:

.Once the hybrid system is running (30/35% media - 65/70% DWC), if you plan to expand one of the systems (because of the market demand), it is necessary to keep that ratio? where does this ratio come from?

.Different designs impact in the efficiency of the hybrid system? What about expanding the system for example with this scheme: 1 media bed - 4 DWC - 1 media bed - 4 DWC etc, Keeping the hybrid bed ratio but alternating the media with the DWC. Maybe with this design (theoretically), you get the benefits of the nutrient retention of the media beds and also you provide the DWC with a sufficient quantity too, and you don't saturate the first groups of media beds and leave the DWC with just the rests of the nutrients. Are we thinking correctly?

.The retention of nutrients of the media beds sooner or later impacts in the disponibility of nutrients in the DWC?

.Do you think that the DWC system is not efficient to grow tomatoes, cucumbers, aubergines improving the raft structure and adding the lacking nutrients? Because this is a creation of an ecosystem, there's a lot of things that probably no one is seeing or studying in the aquaponic water.

Sorry for so many questions but we are in the aquaponic journey and we want to do it right!

Thanks for everything again! 

Mahalo!

Gabriela, just remember that size is not an issue in aquaponics because the main actors are microscopic.  You can scale up or down, then it just becomes an engineering issue to move the water around. Each pound of fish needs 10 square feet of filtration surface area for the bacteria to grow on... this is accomplished by having a bio-filter tank or a media bed. With some careful plumbing planning you can take tanks, grow beds or filtration off line to make a system modular. Start small and scale up... It isn't really a good idea to go big before you have some experience. Try not to think too far ahead and just get your hands wet sooner than later. Take the time while you are learning to explore your market to see what people what and who you will sell to.

Yes, Gabriela these types of systems are relatively new and as I stated earlier, hardcore data is lacking (unlike the 25+ years of compiled UVI data).

What could happen "mixing both wonderful resources in the long term"...is if you become too enamored with the fish and do not keep a light enough load...say much more than 1.2 to 2 kilos of fish mass per m2 of raft space, you run the risk of solids build up in your beds over the long term. If you plant your media beds heavily with fruiting cultivars that have large root mass, and do not take measures to contain, or be able to easily extricate those roots when the cropping cycle is finished...you will only compound the problem of solids build up.

There doesn't seem to be much "nutrient retention" going on in the media beds that is also not plant bio-available in the DWC rafts. Unless you count the unavailable nutrients locked up in organic molecules (solids). Once those plant essential elements are freed up from those big clunky organic molecules and are reduced into their most basic ionic form, they are in solution. Once there is enough of a given element in solution, and it is kept that way, there is no 'retention' going on in the media beds that will 'starve' your DWC. It doesn't really work that wway.

Yes, you should try to keep that ratio (unless you want to start removing solids). That ratio comes from me (so use it if you want to, don't use it if you don't want to...it is what it is)...after trying to quantify the mechanical filtration needed for such a system who's feed input is based upon N content of said system with the understanding that other essential elements will be partially supplemented through buffers and other inputs (salts for fish health etc...), also taking somewhat into consideration the biological component/function that worms (E. fetida) and other non-ammonia oxidizing microbes will play in the reduction of solids...and that you are being intelligent about your feed input and avoiding feed from manufacturers who use non digestible fillers (like feather meal) in their formulation, as these will result in more worthless solids. It's why I don't like the crappy Purina Brand Aquamax feed that is somewhat "standard" in the AP world. You would be better off with a higher quality (less fillers) feed like Skretting. Using a method like the 'dual root zone' thread that I linked earlier will go a long ways in keeping dead root mass out of your beds. This keeps the mechanical filter/bio-filter (media beds) nice and clean for much, much longer.

You can regulate your nitrate production by using a higher, or lower protein content feed as well. Higher protein equals more nitrates.

If you use an indexing valve http://stores.atriaaquagardens.com/1-6-outlet-hydro-aquaponic-index...

you wont "saturate the first groups of beds" since all the beds are receiving the same water out of the same fish tank equally (in sequence).

Yes, it is modular and you can add media beds and/or rafts as you need expand.

No, I don't believe that you are quite thinking correctly about the matter. If sized/ratio'd properly there should be just as many nutrients in a form which is bio-available for the plants in the DWC as there are in the media beds. The media beds retain solids, not nutrients. Those solids need to undergo a process of mineralization in order to useful to the plants. Once they do, they will be just as available in the DWC as in the media beds.Very ealy on if your SOP (standard operating procedures) are lacking you may experience slight deficiencies in the DWC but not in the media beds. This is because unlike water, most all types of common substrates (with the possible exception of perlite, and certain types of sand) have a certain degree of CEC (cationic exchange capacity). But this situation is not the normal system state, but can and does happen in certain situations (easily corrected once their is enough of the lacking essential element present in solution).

Yes you can grow both tomatoes and cucumbers in rafts...you need to provide the vining plant with proper structure. You do however lose the mobility of the rafts. Here is a pic of some of my cucumbers in such a raft.

Here pictured below are cucumbers in a scaled down version of my system that I built for a client...It's a smaller version of the system that's on my property...the system component ratio's are almost identical though...just smaller.

This picture was taken a little less than 7 and a half weeks from planting these seeds (in a relatively brand new system). So these results have been replicable with this system design and SOP's. (Which is somewhat promising...but like you say these types of systems are still new...3-4 years old only)...

I might try to compile some of these design/SOP principles of mine with already published data from other folks into a (hopefully understandable) format/presentation for this years AquaFest. Thank you Gabriela, for providing me with the idea for a topic. I was wondering what the heck to talk about this year... 

I agree, there is much that nobody is studying or seeing in the AP world...

Good luck 



Gabriela Lagrange said:

Hello Guys! 

Now this is interesting, at least for us!!! (Jonathan, we are in the same situation but a little bit further south, there's no aquaponic culture here, there's no commercial scale aquaponic at all. We contacted one guy that studied in the UVI and he is more interested in the fish than in aquaponics, we felt he was not interested to help or give any advise, so we are home alone!). It takes time to spread the importance of growing organic and healthy food (this country is undeveloped in so many aspects).

We've been doing some research and studying the hybrid system that you proposed. We found that this type of system is pretty new and there's no big commercial scale with enough experience to know what could happen mixing both wonderful resources in the long term.

We have some questions:

.Once the hybrid system is running (30/35% media - 65/70% DWC), if you plan to expand one of the systems (because of the market demand), it is necessary to keep that ratio? where does this ratio come from?

.Different designs impact in the efficiency of the hybrid system? What about expanding the system for example with this scheme: 1 media bed - 4 DWC - 1 media bed - 4 DWC etc, Keeping the hybrid bed ratio but alternating the media with the DWC. Maybe with this design (theoretically), you get the benefits of the nutrient retention of the media beds and also you provide the DWC with a sufficient quantity too, and you don't saturate the first groups of media beds and leave the DWC with just the rests of the nutrients. Are we thinking correctly?

.The retention of nutrients of the media beds sooner or later impacts in the disponibility of nutrients in the DWC?

.Do you think that the DWC system is not efficient to grow tomatoes, cucumbers, aubergines improving the raft structure and adding the lacking nutrients? Because this is a creation of an ecosystem, there's a lot of things that probably no one is seeing or studying in the aquaponic water.

Sorry for so many questions but we are in the aquaponic journey and we want to do it right!

Thanks for everything again! 

Mahalo!

Hello Guys!

How are you? We've been doing more research and studying as always! How was the AquaFest? Really niiiceeee aquagarden !!! I want to see mine like that!!! 

After several discussion we decide to go for the hybrid (of course if it possibe and doable here)! 

I attached a global design we are working on. We plan to do the complete system in stages, but we need a general picture of what is going to look like when completed. We are going to have:

Media Beds x 2 (20m x 1,1m = 22m2 x 12" deep) 44m2 

DWC x 5 (20m x 1,1m = 22m2 each bed) 110m2  

Total grow space 154m2

Fish Tanks x 3 (at least 5000lt to supply the system)

Ratios that we use:

Fish: 154m2 grow area (Media+DWC) x 1,5kg of fish mass: 231kg of fish mass

Fish kg/fish tank (lt), we know that in a DWC we visit in Hawaii, they use 1kg fish/16lt water, and in media systems we read that the usual ratio is 1kg/40-80lt (following 1:1 ratio, not our scenario). Now, in a hybrid system what is the proper ratio to use?  Should I calculate an average from both?

Fish feed/m2 grow area = 3kg per day (10/20gr x m2)

Basic Idea

From fish tank to media by gravity feed. We will have 2 media beds (each one divided in 2,5mt = 8 media compartments per bed) with auto syphon each. 

The water from the media beds drains through the syphons to a common pipe (gravity) to the DWC beds. After the last DWC the water goes to the sump and back to the fish tank.

Technical issues...

Fish tanks. With 300kg mass fish that would need almost 5000 lt we have the system nourished aprox. We don't know what work best, to have bigger fish tanks (not full capacity) for future demand or to have the tanks size (exact amount needed) for the actual system and see what happens in the future? Also having more than one tank makes growing/harvesting fish easier. 

What tank configuration do you think can work for us?

Media Bed. Do you know if there's a limit in the length and size of the media beds. As we told you, we think on dividing the 20mt media bed in 2,5m compartments, so we can work independently and for a better water flow and volume (pump).

Do you think we need an independent sump for the media beds? or with one sump at the end of the DWC back to fish tank is enough?

In between the media and the DWC should we put a clarifier or filter? Or with the bio-filtration from the media (with worms) it's enough?

Sorry for so many questions, but there is a biiiiiig difference between reading and action, and as no one can help us here, sometimes it's hard to put it all together!! We are trying to really understand it (otherwise it won't work) and we still need to go fundraising to make it real (now it's the moment because there is people interested in the project, so we don't have a lot of time for experimentation although we know it is necessary).

Thank you very very much!

Have a nice day!

Gabs

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