I.M.T.A. - Integrated Multi-Trophic Aquaponics (my concept)


IMHO, following the land-based aquaponics movement is a necessity. By expanding it, in coordination with biogas production, waste-handling and standard hydroponics, we can do more, with less.

The model I am trying to develop, at home-scale, is primarily to handle animal and food waste. A biogas digester will treat the wastes, producing an organic effluent, that is nutritious to plants and effectively free of pathogens. By ‘effectively’ I mean that, according to the documentation I’ve seen, the counts are so minuscule as to be undetectable, yet no lab will certify it is 100% free of pathogens. The simplest way around that is an additional treatment by storage (sealed and anaerobic for 30 days at comfortable temps, less at higher temps), or other means (chlorination, irradiation, etc.).

So far, I’ve described waste handling, and using the effluent in hydroponics. This is a simple process. To get Aquaponics, you have to include fish and re-utilize the fish wastes, as well… Since the hydroponics will only use ‘X’ amount of the effluent, the balance can be used, in less complicated hydroponics, to raise Duckweed.

Duckweed is a very adaptable waterborne plant. It has oil that can be pressed, for biodiesel, the resulting mass, when dried is high in protein. It is edible and used raw, in salad, etc.

Some fish are omnivorous. Tilapia is the typical aquaponics fish, though others are also used. My personal choice is the Rio Grand Cichlid/Texas ‘Perch’ (NOT a Perch, but actually a native, distant cousin to Tilapia).

Basically, for aquaponics, fish eat and piss and poop in their water, the water is used as hydroponic plant food.

For open-sea pens, multi-trophic aquaponics relies on the same concept, but it’s more of an open loop, allowing the water to go pretty much wherever, bring in new nutrients and washing out some nutrients.

Each section of my concept works, and is in practice, in various places. I’ve just stacked the process, to use the nutrients in a more intensified manner.

Macroalgae-Kelp… Kelp farming and Kelp as fish food is already in use, as is feeding Kelp to Abalone, in floating cages. Abalone yielding Mother of Pearl, the occasional pearl, and some great meat, as well.
( http://videos.howstuffworks.com/discovery/28310-dirty-jobs-feeding-some-abalone-video.htm )

This would be floating above the fish pens.

Top pen would have a feeder species of fish, that consumes kelp. The middle pen (conjoined), holds the market fish, which are routinely fed a portion of the feeder-fish. The bottom pen holds a shellfish/bottom-feeder, such as prawn, crabs, or even lobster. Any dead fish, from the other pens, can be chunked and fed to the bottom pen.

Now, not quite done… As the poop trickles down, it is collected, from beneath the shellfish and pumped back up, as food for the kelp and additional food for the Abalone.

Summing up, by raising kelp, feeding it to Abalone and feeder-fish, the IMTA should produce a reliable source of Mother of Pearl and Abalone meat, a Marketable fish, and a shellfish. By having a number of these, at various stages of development, there is a steady supply to market.

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(Wilfried Ellmer) #2

@JL_Frusha, you seem to have given a lot of thought to sistem integration between a habitat structure and aquaculture do you have pictures to explain the concept ?


What I have not described above is the general arrangement of supply.

Most trawlers have a hold capable of containing various amounts of fish, on ice, in one or more sealed compartments. As long as it’s coming for the market fish, it can serve a dual-purpose of resupplying the stock of feeder-fish and market-fish fingerlings.

Coastal areas tend to have commercial hatcheries, especially for stocking existing commercial fish production, so it is only necessary to enter the supply-chain, in many places, however, it may be advantageous to enter agreement to produce the feeder-fish, if they do not have a suitable species in production.

Offload the feeder fish, load the market fish, offload the fingerlings., top off with more water and aerate the hold, filtering the solids, on the go.

This serves a dual purpose, for the market fish. Generally, ‘finishing’ fish for market is a 3-5 day period without food, so their intestines are empty, reducing the tendency of contamination and making for easier cleaning. It also delivers live fish, rather than requiring immediate handling.

The process is equivalent to finishing fish from less than savory waters, by placing them live in a holding tank and flushing fresh well-water through the tank, to help remove bad flavors.


It’s what I tried to describe and cobble together for Mattias to work with, if he was interested. I am not any sort of artist. That lies beyond my ability and beyond both my computers’ capability and my capacity to learn. I passed both a drafting and a CAD class, about 30 years ago, with extensive assistance.


Now you tell me those weren’t perch! Long, long ago, I ate a few of those. Not my favorite fish, bony as I recall.


If you ate “seabass”, no telling what it was.


@Kat, nobody ever said these fish were seabass, totally wrong shape, but were supposedly “Perch.” My dad worked on the Apollo project, and we moved to Texas, very close to Johnson Space Center in 1966. For an L.A. kid, the idea of open water – lakes and bayous-- was a new, interesting thing. As was fishing. What I caught most often were what I was told by the local folk fishing were Perch.

Aerospace contracts come and go; we were only there for a year. (When TRW lost the LEM contract my dad was on to (I think it was) Grumman. I never fully adjusted; it was a strange cultural experiment, mostly forgotten once we returned to California.


Tank-raised Rio Grand Perch/Cichlids are at least as good as Tilapia. Kids caught some, out behind the house (we rent, along the Colorado River, East of Austin). Raised a bunch of 'em in a 4 ft dia, water trough… :wink:


Probably was real perch. We used to catch 'em all the time. Blue Gill tend to be larger and have more meat. Rio Grand Perch have only recently been introduced in slow-water areas, to control… du-du-DUH!.. Duckweed… Know of both from personal experience, which led to research, which led to dinner…

Not my pic…
Rio Grand Cichlid

Yellow Perch



Funny, i didn’t say those were seabass either!


Open-water, captive fish rearing, using grain-based feed is the current normal practice. While the pens and anchoring methods are adaptable, they are unnecessarily unfriendly to the environment. Many are reducing corn-based feed composition, and increasing the utilization of fish-processing wastes.

Since the Pacific Northwest seems rather free of typhoon/hurricane activity, I’ve begun contacting various organizations and researching the literature available.



Thanks for that link! Exactly the kind of info I was wanting to read.

– Larry

(Jonas Smith) #13

Great info. I’d love to know some of the pricing for the Sea Station and Aquapod options…that’s a lot of metal…

EDIT: This is from 2010, not sure how pricing has changed in 5 years. $140000 each for a 3,600-cubic-meter AquaPod


Sounds like 1) someone had money to get rid of before taxes, 2) disinformation to scare possible competitors.

Last year, someone sent me a few pics of giant buckyballs being built on shore in Japan, for use in fish cages offshore. They used two very large and pricey cranes , plus people holders, to assemble these, then put them on huge barges with cranes, then $million towboats to take them out and place them in the water with floating cranes. Being not TSI-oriented, i went outside, grabbed a 4ft length of such steel tubing, duct tapped the ends shut and put it in the pool. It floated. That one fact alone eliminates the need for on-shore fabrication, huge barges, multiple huge cranes, and huge towing fees. Put your ends on the raw tubes, toss them into the water, drag them out where you want the cage, assemble the ends on the surface, sinking each node as it’s done, you can do it all with 4 people in two old “bass boats”.


The buckyball method works, well, as a single pen. To do the stacked pens, it takes a different model. I can hang stacked pens off a spar-buoy, as others do, with single pens, just need a longer spar-buoy and deeper water.

Almost everything for the system I have in mind can be purchased, in one for or another, and adapted. Problem is the cost of those things, vs real-world diy, build it at sea, ferrocement, can do. Once the first spar is done, and seeded, the next one can be made, until you have to number necessary for the rotation and any additional ones, with housing, can be built, or whatever order.


The url Jonas posted mentioned the EEZ of the usa is just too onerous for a business. You cannot fish farm, you cannot commercially otec. It really is a case of “who is John Galt”.

I suspect your bigger problem, once you have a seastead you can live on outside the EEZ, is being an importer (even if a usa citizen on a usa registered “boat”). The biggest issue is just being out there. Next is getting product back to shore. Especially before it dies or goes bad. And make a profit.

Have you run the numbers for having your living space already outside everyone’s EEZ, starting with one cage (of whatever plant and/or animal in it), the cost of growing it, getting it to market, and getting back to the seastead? After all, 200 miles is a full day at 10 knots (both directions?). Plus you will be drifting in deep ocean, so your distance to market is always increasing. I know you have considered most, if not all, of these factors, but as that urls says, it’s just not worth it to be inside the usa EEZ as an ocean farmer.


I don’t have to be outside the EEZ, to live, or prove it works. As a disabled veteran,I have my own needs and that has to be a priority. It’s also where my steady income is from. I have to have prescriptions filled, see Dr.s, probably more so, than anyone else I’ve met in the forums, old, or new, but, I’ve survived 6-8 strokes, have a bad back, chemically induced asthma, etc., so, until they put a major medical facility on floats, I’m going to continue to use regular facilities. SeaTac has several military bases, there are also VA facilities, so I’m covered. There are major fish processing plants in the vicinity, as well.


This price may be old, but it’s a starting point for an instinctively-quantitative guy:
That price works out: ($140,000 / 3,600 m^3) to roughly $40 per cubic meter of “cage.”

So this gives us a mark to aim at and exceed. It also gives us some idea of the profit potential. If any are selling at that price, it seems to me that there are probably places where cages like this can raise enough fish/shrimp/whatever to pay back that investment.

I think that price per volume is high, and good engineering (and/or competition) ought to be able to bring that price/volume down, significantly. At which point, there will likely be more locations where aquaculture will be profitable.

So far, I see aquaculture as being one of the more likely nearer-term ways for a seastead to generate cash flow to pay for the non-oceanic resources it needs, especially during the bootstrapping phase.

I’m unpleasantly surprised to learn that the US’ rules/regs have made this kind of aquaculture infeasible in so much of the US’ EEZ. But the US EEZ isn’t the whole world.

An earlier post seemed to suggest that the Feds don’t get much involved for sites closer than 3 miles to shore. Are those waters under the control of the state? Are any states acting in aquaculture-friendly manners – specifically friendly to moored cages like this, out in navigable waters, but less than 3 miles offshore?


That cost should be considerably lower, but it’s paying for a name and a novel approach, mostly in a high-rent neighborhood (Hawaii).

If experimentation bears fruit, per the documents I’ve linked in the geopolymer thread, then the cost of the spar-buoy, itself, can be considerably lower, using something more permanent, and far less energy intensive, than stainless steel. Diatomaceous earth, high alumina clay and many caustic (alkaline) substances are considerably cheaper than stainless steel.

What may, or may not be feasible within the US EEZ, probably has more to do with permits and competition, than any single other factor. How many hoops and how fast can you jump through them?

The biggest hurdle is making the fish-food and the nursery stock supply practical, and working with a commercial nursery will play a key role, as will planning the whole project, so that there is a ready market for the live seafood. With a decent commercial partnership, there would be industrial pressure to apply, in order to get approvals.

Building a floating structure is one thing, turning it to a commercial use is and entirely different matter. Once built and the Kelp has been established, the next phase would be to add the Abalone, then the feeder fish, then the market fish. You would want the environmental controls and primary food supply in place, first.

Once the kelp bed is established, the growth rate can be projected, allowing a better estimation of the number of abalone and feeder-fish can be supplied. Once that is established, a known feeder-fish production rate will allow the initial estimation on the market fish numbers, always keeping in mind that, as you add each level to the I.M.T.A., the wastes will also interact to alter the production and the environment.

Ultimately, by cutting out the cost of land-based feed, completely, having a ready supply for stock and a ready market, then expanding the capacity to meet demand, will be the best way to commercial feasibility.

The kelp will support only so many Abalone and so many feeder-fish. Those feeder-fish will only support so many market-fish to maturity, the feed wastes will support so many crabs.

Once one I.M.T.A. system is established, routine operating procedures are developed and in place, the construction of the next system can begin, until the total reaches a maximum capacity for the initial manpower. That will lead to the numbers necessary to maximize the market-share.

Increasing I.M.T.A. will also impact commercial fishing, so initial efforts to establish a replacement for commercial practices should be made in such a way as to maximize current resources. Trawlers already have the capacity to carry market fish to the processing facilities, as well as their preferred places to sell their catch. By utilizing those trawlers, and their connections, it should mitigate any industry concern of farmed-fish displacing traditional methods.

As a byproduct of the I.M.T.A., each set of pens should become its’ one mini-habitat for other species, creating sports-fishing and sports-diving destinations. Being able to rent a spar-buoy motel suite may become an additional source of income.

Flexibility of the operators and the ability to find a wider variety of ways to explore marketability options, in innovative ways, will ultimately determine the success or the system. It is even conceivable that other marketability options could displace the commercial fish production, as a destination mini-resort with its’ own supply of fresh seafood.

Imagine a ‘canned-hunt’ system, where divers can enter a relatively safe (namely predator-free, enclosed/caged) fishing preserve, where they can spearfish for one of several species of fish, capture their own crabs/lobster, etc. Those with the ability can prepare their catch, or they can turn it over to the staff to become a professionally prepared individual meal, or catch of the day.


Can you comment on the size (or size range, if different) of the holes in the mesh or netting you’re planning to use? I’m wondering about water forces and what sort of average current is desirable, tolerable. Any thoughts on mesh size?