Aquaculture - Aquaponics without Plants

[mornings]

Hi,

Periodically, I speak about the notion that aquaponics is not the only way (and quite possibly not even the best way) to integrate fish and plants.

In the rush to embrace aquaponics, we sometimes overlook the fact that you can grow fish without plants......and that there may be good reasons for doing so.

Long before there was aquaponics.......there was aquaculture.

mornings has pondered the same question so I moved his post here to enable it to be discussed in its own thread.

Gary


Gary,

While fish are not my bailiwick (I do enjoy eating them), I've given some thought to growing them in a system that has gravel beds with worms only in them (no plants). The gravel would provide home for bacteria to turn fish urine to nitrites to nitrates and worms to turn the fish solids into nitrate and various other nutrients. A reverse osmosis filter would take all these out, leaving the fish with nice clean water.

The whole fish system could be housed out of the sun, even underground, certainly out of valuable growing space; maybe a place more temperature friendly to fish. Since the comfort parameters for fish fit well within those of worms, temperatures and other conditions could be keep more easily ideal for fish.

What little experience I have with RO filters indicates low energy usage, low maintenance and relative low cost. It does add a new technology we've not normally used and metrics not explored. Any one have any knowledge on how these might work out? Are there better alternatives?

Then, the nutrient could be fed into any one of many hydroponic configurations, the size being independent of one fish operation. Maybe some of you enterprising fish growers, who don't want to be bothered with plants or don't want to match plants with fish volumes, could sell your nutrients to hydroponic growers.

Not sure this makes sense for a small system with both separate components as it would seem to create more overhead. Then again, one might be able to grow fish in one's basement and place the plants in a hanging hydroponic unit in the living room window.

Since you apparently have at least experienced and become ware of some of the agony of an integrated system, what say you? Anyone, thoughts, ideas?

M

[GaryD]

Hi mornings,

I'd like to commence the discussion with a consideration the reasons that you might want to raise fish without the use of recirculating hydroponic growing systems.

1. You may be able to acquire your vegetables in other more cost effective ways.....eg....your family might operate a market (truck) garden.
2. You may be an accomplished organic gardener and not wish to change your growing methods.
3. You may want to be able to treat infestations or diseases in one or the other of your plants or fish without affecting the other.
4. You may want to avoid the pH and temperature compromises that are necessary in recirculating aquaponics.
5. You may live somewhere where you have freezing winters where vegetable production is not practicable.......or (like me) where growing at the peak of summer is seriously diminished because of insect infestations.
6. You may find it easier to minimise overnight heat loss from your system by separating your fish system from your growing system.
7. You may want to grow fish and vegetables with a lot less set up work......and expense......by using a simple recirculating aquaculture system in conjunction with growing systems like raised sheet mulch beds, square foot gardens and wicking worm beds.

That will do for a start. Can other people think of reasons/advantages?

Gary

[Ravnis]

I have trialed growing fish in a greenwater culture with the algea growing to be the means of nitrification. It has worked well, but growbeds will not function with the thick solid mass that the agae forms.

I have set up a series of tubs that let the algae settle out of the water and pump it back into the tank. While I can't directly hook up grow beds to this system, I have found two good uses so far. One is that my ducks go wild for the algae and the red midge fly larvae(blood worms?) that grow in it. The other is I throw it on my small trial wicking worm bed and the growth is good. I have a watermelon plant that has vines that are ~10ft long and has produced 3 medium sized water melons. The worms either eat the algae or the bacteria growing on the algae. The only main issue I have had has been aphids, ants, and grasshoppers.

The ph of the water runs around 8 and will raise back to that in a matter of hours even when acid is added to bring it down. While I like fish, I am currently considering replacing them with ducks if I can figure a way to handle the solid dirt and feather issues. With ducks, I won't have to worry about water quality as much or low oxygen conditions at night and pumping( also known as energy costs) can be kept minimal.

I did try using the water from an aquaponic setup in just a hydroponic setup, but growth was dismal as compared to being setup with the tank. My theory is now that it is not the elements in the water as much as the microbiology there that explains the fanstastic growth in an aquaponics setup. This also explains why in several experiments the growth in an aquaponic setup did not take off till the second year.

[mornings]

Gary,

Wow, good points.

The one thing, a question really, raised in my mind was, of all the aquaponic work done over the last decade or so, no one seems ever to have analyzed the fish effluent to see what they are actually feeding the plants. They just seemed to have assumed that the effluent would provide a complete plant diet. As thorough as Dr. Raboky is, I've not seen anywhere he covered the subject of nutrients except very vaguely, mostly centering around nitrate. (If I am ignorant of such work, someone please inform me, Please.)

None of this is to say that such fish effluent can't provide a complete diet for plants but there has got to be a lot of variation among different fish species, different fish diets, etc., without any idea which one(s) is best, most efficient or how it can be modified. It all just seems to have been guess work. Am I wrong?

And, I have to admit, it never occurred to me to analyze effluents until I began to investigate hydroponics. Hey, after 6 or so decades, I think these folks know a thing or two (just a little misguided about using chemicals).

For example, DR. Howard M. Resh's "Hydroponic Food Production" recommends:

Ca: 180-200 ppm
mg: 40-50 ppm
K: 210 ppm
P: 50 ppm Ammonium-N: 15 ppm
Nitrate-N: 165 ppm
Fe: 3-5 ppm
Mn: 0.5 ppm
Cu: 0.1 ppm
Zn: 0.1 ppm
B: 0.5 ppm
Mo: 0.05 ppm

Any one know how this stacks up with what they are doing?

Interestingly, all this has rekindled my interest in fish. Now I think much of what I have learned with worms may well pay off with fish.

But, while I think this discussion presents us with potential opportunities, the critical element that is not established yet is, how do we take the nutrient out of the effluent water in order to use it separately? My guess is reverse osmosis. The reality is, I don't even know yet if is practical. Anyone?

m

[GaryD]

Hi Jim,

The one thing, a question really, raised in my mind was, of all the aquaponic work done over the last decade or so, no one seems ever to have analyzed the fish effluent to see what they are actually feeding the plants. They just seemed to have assumed that the effluent would provide a complete plant diet.

I get the feeling that a lot of it has been the outcome of growing trials rather than laboratory analysis of nutrient levels.

I find it interesting that when an EC meter is used to measure AP water it invariably reads way below what hydroponic nutrient solution does.....and yet it still grows plants......and often very well.

Some people suggest that it is the microbiology associated with an AP system that accounts for the difference. Dr Nick Savidov has written about how the performance of an AP system lags that of a hydroponics system initially but that the AP system overtakes the hydro unit after a year or two. That supports the idea that the microbiology in an AP system may have a bearing.

I hear the term "unidentified growth factors" used from time to time and I must confess that makes me a bit nervous.

Like you, I'd have thought that some researcher would have described exactly what it is that makes plants grow in an aquaponics system......particularly since it's not possible to make parallel comparisons with hydroponic nutrient solutions.

And, I have to admit, it never occurred to me to analyze effluents until I began to investigate hydroponics. Hey, after 6 or so decades, I think these folks know a thing or two (just a little misguided about using chemicals).

I agree......hydroponics seems to be a far more exact science than aquaponics.

But, while I think this discussion presents us with potential opportunities, the critical element that is not established yet is, how do we take the nutrient out of the effluent water in order to use it separately? My guess is reverse osmosis. The reality is, I don't even know yet if is practical.

RO is one possibility. Two things to consider.......it takes pressure to force water through the membranes in an RO unit and the bit that you want to keep (the stuff that the RO unit filters out) is removed from an RO unit by back-flushing with plenty of water.....the reverse of what you are trying to achieve. The upside is that you will also have some very clean water as your "waste" product.

You could grow algae......

• The creation of algae sees the solids in the water undergo nitrification and, therefore, turned into plant food.
• This could be applied (as a liquid slurry) directly to plants/
• There are other uses for algae (of particular types) - as food for humans and micro-livestock and fish.
• Some algae contains high concentrations of oil......and can be pressed to separate the oil for use as fuel.
• The algae could also be put through an anaerobic digester to mineralise it further. The concentrated liquor could be decanted for use in an hydroponic growing system and the sludge could be fed to worms and converted to castings (and even more fertiliser) and worm biomass (for micro-livestock and fish food).

Gary

[mornings]

Some people suggest that it is the microbiology associated with an AP system . . .I hear the term "unidentified growth factors" used from time to time and I must confess that makes me a bit nervous. . . Like you, I'd have thought that some researcher would have described exactly what it is that makes plants grow in an aquaponics system......particularly since it's not possible to make parallel comparisons with hydroponic nutrient solutions.

Gary, the following is a condensation of something I wrote on an AP list but thought it appropriate here. It has to do with the ancillary subject of nutrients.

To my engineering mind, we should know (as well as the hydroponics people) what is in the water we are feeding our plants. Disappointingly, all I find are rather bromides like, "the plants are doing well, it must be good". As warm and homey as much of this sounds, none of this takes into consideration many of the variations of circumstances and environments in which many of us must grow. It's nice to see pictures of a mix of healthy veggies but there are rarely any stats with them to tell us what the plants are doing year round, how productive they are on an ongoing basis and, most importantly, why and how they might be so. With all due respect, even Raboky is pretty light on such details when you compare the work done by hydroponics people.

I think that if separation of the two aquaponic functions could take place, in order to truly capitalize on it, we must know what is in the mix. I grant you, there are likely elements of aquaponics that are simply not the same and much more than putting elemental water soluble nutrients in water, but I think at a minimum we should know what those elements are and how they get there.

Let me explain at least one reason why (there may be others -- I can probably count on you to give an exhaustive lists): Since most nutrients come from the feed for our fish (I realize there are other organic elements like lime and various rock powders that might be used to supplement), one simply can't get more out than one puts in, no matter what the mystical powers of aquaponics are. And, like the various circumstances and environments, feeds are just not all the same. And, unlike the hydroponics inputs, feeds do not come with a list of elemental nutrients -- one must guess or hope. This is an issue not unlike that of the organic farmer. I mean, are there successful organic farmers who do not do soil analysis? I don't think so.

Also, by understanding what we get out vs what we put in, it is just possible that we can better control both the quantity and rate of nutrients, which I think will be necessary if we hope to leave some of the downsides behind of combined functions and capitalize on the benefits of separation.

Does everyone using aquaponics have to use and be aware of all these vicissitudes. No, let's hope not. But I think someone needs to establish them, otherwise, what goes on as grower information is just swapping stories.

m

[GaryD]

Hi Jim,

A commercial aquaponics operator couldn't afford to take a chance (I'd have thought) so they probably do one of two things.....get a nutrient analysis done or treat the water as plain water and dose it with nutrients accordingly. Anything else would be risky plant business.

To be candid, with all of the stories that abound about people using Seasol/Maxicrop or similar, I question how successful this 'hit and miss' approach to AP really is. We know that most commercial operators dose with calcium, potassium and iron.

If you're not running multiple tanks that are networked with each other, you must go through a too little/just right/too much stage with every crop of fish that you grow.

In the absence of laboratory analysis, your only safe bet would be to assume that you're short of something and dose with a general purpose liquid fertiliser......which is what is already happening with users of Seasol and Maxicrop.

Interesting stuff, Jim.

Gary

[mornings]

Gary,

In my experience with soil testing (to grow organically) I find after testing, when I am setting up a new plot or if I am changing or switching from perennials, after a season or so testing, I no longer need the testing. It's as if one creates an intuitive baseline. After that, unless some new variable gets thrown in, like a disease or pest, testing is no longer necessary (I find that with organic growing that such variable don't show up nearly as often as they do in conventional ag). One can simply make adjustments based on previous experience. Call it an empirical approach.

Just as valid is to look at someone else with similar experience under similar conditions. This is the saving grace of organic gardeners. I think this should be valid for small APers. But, in the world of organic gardening one can go as deeply as one wishes into the mysteries of soil science.

This level of water science (if you will) is simply not available. So far, it seems to me that all we have in AP is that empirical & intuitive approach, but without much real science behind it. We jsut keep swapping stories.

There may be commercial operations large enough do this kind of investigation who horde the information, but I am doubtful that it happens at all -- if so, I suspect there would be a lot more commercial AP operations, assuming good, complete information would lead to better profits and, thus, more such operations. It is this kind of information and sharing that has built hydroponics into a major source of fresh food.

I know UVI has received US federal funds to put out much of the information they have disseminated. But the interest seems to have dwindled. They hawk their courses, but they are doing the same thing we are all doing: "see if I do this , then this is what happens". There are even consultants who will take your money for such as this.

I guess there is the possibility that AP itself is simply not as good, efficient or profitable as proponents have suggested. I'm not willing to admit that -- yet. I still think it is the farming and gardening of the future. The other possibility is that the information is out there but I haven't found it. Maybe there is just not the critical mass of in interest yet to create concepts and research needed.

Well, we keep trying. I remember trying to get farmers to grow organically back in the early 80s. I had gov't officials tell me organic would simply never happen. Those same officials sing a different tune today.

At least the hydroponics people are not hostile like conventional farmers were (many still are). They seem willing to share what ever information they have and embrace anything that will work. Unfortunately, that may an indication in itself that AP just isn't there yet. When the HP people start lining to to do AP, we'll know AP has arrived. But it ain't gonna happen until we can start getting the basic nutrient information that the HP people have had for decades.

m

[GaryD]

Hi mornings,

I guess there is the possibility that AP itself is simply not as good, efficient or profitable as proponents have suggested. I'm not willing to admit that -- yet. I still think it is the farming and gardening of the future. The other possibility is that the information is out there but I haven't found it. Maybe there is just not the critical mass of in interest yet to create concepts and research needed.

One thing is for sure......we have to break out of the limited mindsets that currently attend aquaponics. The problem is that the discipline (if I can call it that) is largely in the hands of small thinkers who get irritable whenever someone suggests alternative ways of doing things.

I think the failure of investors and credible researchers to embrace aquaponics in the same way that they did with hydroponics.....in the face of so much misinformation and resistance to change........is not only understandable, but prudent.

At least the hydroponics people are not hostile like conventional farmers were (many still are). They seem willing to share what ever information they have and embrace anything that will work. Unfortunately, that may an indication in itself that AP just isn't there yet. When the HP people start lining to to do AP, we'll know AP has arrived. But it ain't gonna happen until we can start getting the basic nutrient information that the HP people have had for decades.

I agree. A quick glance at any hydroponic magazine will satisfy the reader that commercial hydroponic growers are tuned into the latest technology and research to support their production efforts......and there's plenty of both to be found.

Notwithstanding the fact that we've had UVI and their work around for nearly 30 years, they are still the main game in aquaponics.......doing pretty much the same thing as they were two decades ago.

The reaction in other places to the discussion on whether aquaponics can be "disconnected" (in addition to the other mythconceptions that surround aquaponics) suggests that we are more likely to be in the dark ages than the renaissance.

Until that changes, aquaponics will continue to be the province of backyarders and a few brave souls who are willing to gamble their small fortunes on (what appears to be) a good thing.

Gary