Backyard Aquaponics
A place to discuss aquaponics

Hello all, signing on from Hanover, New Hampshire, USA. I'm a PhD student who will be working on sustainable food production systems. Our lab is interested in integrated systems, and we are in the process of setting up a simple experiment for this summer. I would love to tap the vast amount of experience that the members of this forum offer in helping guide some of the questions that we may be asking, and to keep from reinventing the wheel. That being said, what do you all see as either 1) the most pressing questions in aquaponics, 2) things that ought to be clarified or scientifically determined (such as apparent contradictions or points of dispute), or 3) anything else? I come from a background in aquaculture, so I am much less up on the plant aspects of aquaponics. One specific question that I would like to pose is this: why not have the plants growing directly on top of the fish tank? I am thinking of John Todd designs (google him) for waste water treatment (and food production). I'm excited to hear what you all have to say. Thanks

Tyler

Hi Ty...welcome

Some people do grow stuff floating on the fish tank. Not all plants like that though...lookup wet feet in the search. Also some fish like to eat the roots, so more care needs to be taken selecting both plants andfish. Use search for floating raft for more too.

For me science questions would include a study of food and drain vs. Contant flood. And a long debated subjuct of actual water use.

We welcome your questions and I'm sure others will chime in with their opinions.

If I grew the plants on top of the tank I wouldn't be able to get the fish out to eat them

Was my grand plan originally but didn't work that well, strawberries are about the only success I had, Earthbound is tinkering with a commercial system that has floating plants, but not in the fish tank, see here viewtopic.php?f=13&t=5209

Looking at your location, New Hampshire, I think a pressing issue is winter. I put up a satellite dish yesterday in a snow squall. The first March in recorded history without snow and we get snow the day before Mother's Day here in Minnesota/Wisconsin. Your post says you are looking at a summer project, but the general wisdom says it takes six months before you get the super plant growing balance. It is my understanding that makes aquaponics a year round project. You can look at slowing it down over the winter, but freezing it solid? There are a lot of questions about greenhouses, the best design and costs. I've spent a lot of time researching greenhouses outside of aquaponics and while I find a lot of claims I have not found any actual data. Obviously there are commercial hydroponic farms that cover square miles in places it snows but they buy materials on an industrial scale. On the other hand the guy at work, his wife gets that greenhouse sheet plastic every fall for free from local nurseries that are tearing down for the season. On a January afternoon her hoop house can get up to 60F, but at two in the morning when it's -20F the inside is not much different. Just some thoughts.

I would like to know once and for all whether it uses less water than a conventional (mulched, drip lined) soil garden.

Hey guys, thanks for all of the comments! First, here is some additional info so that you have a better idea of the situation. First, I'm from Duluth MN so I'm sending a big "you betcha" to those who mentioned concern about winter. Second, the issue of water usage is important, yet overlooked here where we freshwater is not at all lacking. That's something that I will definitely keep in mind during this. Where I am thinking about taking this is towards looking at the nutrient cycling, utilization of natural feeds (plankton, biofilms), and multi-trophic/ multiple species systems. We want to think about very ecologically-based, resilient food production. We are interested in floating the plants in the tank to avoid having to pump water in hopes of using as little energy as possible.

The purpose of our research will not be to perfect aquaponics systems; you all are in the process of doing so right now. We also have quite a few resources available, and we don't have to make a profit (or break even). While this makes our situation unrealistic, it does allow us to experiment with different ideas without that monkey on our backs. Also, we always keep in mind the fact that what is unprofitable today (due to cheap energy, cheap agricultural inputs) may not be in the future.

My next question for the forum is, does anyone work with green-water or natural feed systems?

Again, thanks to everyone and please keep the comments coming. I really appreciate it.

Tyler

Hmmm. Floating the plants in the tank? Thats not normally how Aquaponics systems work. The main issue here is the fact that we need to get oxygen to the roots of the plants to prevent root rot, and the fact that at the core of our systems are the bacteria which handle the Ammonia->Nitrite->Nitrate conversions.

Obviously home ornamental pools use this method where true aquatic plants are grown directly in the pools. But only things like lily's, irises, water mint, water hyacinth and other aquatic plants are effective grown like that. We have a tendency to concentrate on more human consumptive plants.

It depends whether you are looking for a truly ecological food growing method, or simply studying aquatic culture. Green water is counter productive to an aquaponics system. Why waste energy feeding the green water algae when you can feed consumptive plants? If you want as little energy usage as possible then you have a very slow growing system. You need an energy input, even if you only use a solar powered pump, to make it work. However the amount of energy needed compared to modern "oil" based farming methods is a lot lower.

Hey Dragon, thanks for the comments.

I get the impression that root rot can be a major problem in aqua/hydroponic systems. What do people do to combat that? Good oxygenation of the water, or exposure to air? Are those two practices actually performing the same task? That's to say, if the water were sufficiently oxygenated, would air exposure be necessary?

In digging through the scientific literature, it has become clear that there is no hard and fast answer to whether plants prefer nitrate or ammonium. I see that some plants may have a preference, but that most plants can utilize both. The question resides in what net effect does nitrogen form have, given that the plant handles them in different ways. Either way, plant roots in the water, the walls of the tank, and any other structure in the water will provide some nitrification. I would definitely expect to see a mixture of nitrogen forms; ammonia, nitrite, and nitrate. Obviously, ammonium is undesirable for the fish, so, for optimal fish production, we would hope that nitrate be the predominant form.

As far as green water goes, we would be producing fish (such as tilapia, perhaps bluegill or other planktivores) that would utilize it as a food source. Also, oxygenation, although tricky, would be another benefit of algae.

I'm going to look into your solar pump idea. We are in a greenhouse, so it certainly isn't an energyless system (solar!). And yes, I am thinking about a truly ecological food production system, not just to study aquaponics or aquaculture. By the way, what I'm thinking about right now is simply a project for the short term to get my feet wet and hands dirty with an integrated system, while also addressing some scientific, unanswered question.

Thanks again, let me know what you think.

Tyler

Tyler,

Sounds like you've got a great opportunity to apply some scientific rigour to this field. Which is great IMO.

Concerns/questions I would like to see explored are:
1. More sustainable feed input. Currently high protein feed sourced mostly from ocean creatures is used. This hardly seems 'sustainable' to me.
2. Water usage for various plant growing methods (+1 Gemmel). Somehow arriving at the same quality output, show the various inputs required for Aquaponics, Hydroponics and soil based methods.
3. Pest control. Is it possible to produce non pest affected crops outside? This is more a commercial concern.
4. To remove solids or simply pump onto growbeds? Another debate here.

I suspect a lot of folks on this forum will have an opinion on these points and are tackling them in their own way based on their experience and learnings. I give them to you in the hope they can give you an idea of experimental approach.

As for your growing plants over the water... good in theory as it maximises space utilisation and creates cover for the fish. Practical considerations I can think of are, any artificial light for the plants not effecting the fish, plant debris dropping into the tank, fish and tank access, oxygenation, safe plant harvesting access ... that's about it.

Good luck, keep us posted.
Pete

If you want fish density in your system you can either pump water into grow beds and let it fall back into the fish tank and gain oxygen that way, or pump the oxygen into the water with an air stone or similar. Either way, a 24/7 supply of electricity is non-negotiable for higher fish densities. At low densities isn't that just pond-based aquaculture?

As for growing plants in the fish tank, have you considered growing duckweed in the tank and harvesting the duck weed as an input to vermiculture? Then feed the worms to the fish? I've read worms are hard on a tilapia's liver, but presumably not on a bluegill. Also, what were your plans for solids? Grow beds work as filters too. And are you more focused on fish or plants? If you're not focused on food quality fish have you considered bullheads? They're damn tough fish that will survive all sorts of water conditions.

As for research parameters it seems most systems are designed for the size of fish at harvest. When the fish are first introduced they are smaller, duh. Being smaller they produce less ammonia and you introduce less feed. As they grow so do the system inputs. This affects several aspects of the water. For example you are losing water to evaporation, the plants and the fish. But you are not losing the non-H2O parts at the same rate, like the calcium carbonate, which should increase pH. Just studying the mineral aspects of the water over time should be very interesting. Never mind trying to normalize your data for all the moving targets related to fish size, plant growth and plant mix, and temperature to name a few. Reaching any sort of true balance without multiple fish tanks with fish at different stages of growth is probably not possible.

And finally, you have seen Growing Power in Milwaukee and read about Will Allen? Jsonline writes something on Growing Power every few months.

Hmmm... some interesting questions posed..

My thoughts... I would be VERY interested in finding more energy efficient means of production... Solar water heating in the winter. Solar/thermal heating and cooling of a GH (though some neat research has been done by http://www.sunnyjohn.com/indexpages/shcs.htm ). Taking that to the next level might be excellent. Also, the soap bubble enclosed greenhouses appear to be highly efficient....

Reducing pump inputs may be possible with careful leveling of tanks and beds... (Thinking beds that are barely above the water level of the tank that flow directly back into the tank...) Careful planning in setup can reduce pump head/power... The best answers for efficiency would be future thinking.

Solar or wind powered systems? Being able to go off-grid would really boost the home producer...

The goal should be finding the magic balance points between production and power consumption...

my 2 centavos...

CB

Looks to me like the world is your oyster as far a aquaponic projects go. There are MANY claims about productivity, growth medium, flood/drain v constant flow, fish species, nutrient level, use of fertilizers, etc. Some scientific rigor applied to any of these areas would be extremely useful.

As for to pump or not to pump, its a non issue with solar cells and battery banks the pumps can be maintained independently from the powergrid. The only question I would ask there is, does the "free" solar power eventually pay back the overhead of production and cost for the components or is this another hidden cost on the environment?

Caribis, I have heard about Growing Power and it seems to be right along the lines of what we're interested in. I'll look more into it though. We have been giving some serious consideration to bullheads, not because we don't care about food quality fish, rather because we think that there may be a market, given the right marketing strategy (although we aren't going to be coming up with one!) We will be using tilapia because of it's ubiquity in aquaculture and because we already have some adults ready to spawn. Native, cool-water fish are a strong interest though; it would likely make a lot more sense in this climate. As far as solids removal and buildup on plant roots, that would be something important to keep track of, and I guess I would hope for microorganisms to be taking care of a lot of that. You bring up a great point about balancing fish and plants that will inevitable be at different life stages. Balancing the system for optimal growth of both would probably be out of the question. Taking from that idea, what if the system were more complex, more like a natural ecosystem? What if there were functional redundancy by having more than one organism filling similar niches? For example, if there are vegetables and algae taking up nutrients, will the system be less affected by the harvesting of lettuce and natural decline of phytoplankton? Hmmm...

Country, I think you're right in that carefully planned systems could show gains in energy efficiency, and future thinking is key to our vision. We aren't really in a position to look at renewable energy design, although insulation and passive solar are low tech ways that we would be addressing the issue.

Speaking of issues, what are the two biggest sins of aquaculture (showing my bias towards seafood production)? Feeds using fish meal/oil, and energy usage. Seafood production with less of those two things is my overall goal.

Here is a pic of what we're working with. Note the "solar tanks." They are made of translucent fiberglass, thereby capturing a lot of solar energy that helps (to what extent I'm not sure) with GH temperature control and allows us to look at more algae production and the increased natural, in-tank fish feed. Thanks again for the comments, and please keep them coming. This is beneficial to hear other perspectives, sort through my own thoughts, and hopefully get other people to think about some of these topics.

Tyler
JK, the pic wouldn't fit on here. I'll take a lower resolution one and get it up in the coming days...

Rob, great point about whether renewable energies are actually "free." I just had a great talk with our farm manager, who is also a lab member, and he was making that same point. How much energy went into producing that solar panel, and where did the raw materials come from? How much petroleum is locked up (literally) in all of our plastic glazing and pvc pipes? Maybe we will go back to pond culture, eh Caribis? Obviously, I'm not going to rule out the use of plastics for our production, but it is something to think about.

Tyler