Backyard Aquaponics
A place to discuss aquaponics

Could any one point me to any posts or research done in the area of minimal or no feeds added to a system and the amount of harvested growth that results. I am interested in how the plants up take of Co2 and the energy it receives from the sun can off set fish food inputs to the system. Ideally a truly "sustainable" AP system where the plants feed fish and humans.

Thanks.

when looking for a "zero input" system you're not going to find much, because that implies nothing going in and stuff coming out...

i've been trying to figure out a type of naturalistic system, where instead of hand feeding the fish nature provides the inputs. bugs and other stuff falls into the system, and organisms life off of that.

this wont go very farm in the realm of fish production... the naturals inputs would be too low, but this could go leaps and bounds for the plant output portion.

small fish eat mosquito larva and other bugs that fall into the system or use them as a breeding ground, then small detritivores mineralize the solid fish waste and other detritus that falls into the system, turning the waste into mineralized nutrients.

you'd have to do your homework, because essentially you'll be building a hybrid food chain, so you'd have to find organisms and microbes that can live happily together. if you mess that part up, you'll end up with your fish eating your detritivores, and the build up of wastes would make the system go anaerobic and crash...

in the states the combination of mosquito fish and gammarus seems to be the way to go... i've seen a system that is unknowing being powered by these two guys... yes, the initial system was built to run off of the nutrient output of a tilapia fish tank, but as the system sat running in the open air, other organisms made it their home... the massive amount of fish poo were an ideal food source for gammarus, which being a crustacean, help the balance out the ph when they die and eat each other releasing their mineralized bodies into the water. the mineralized calcium helped to offset the acidic nature of the fish urine.

basically you'll be building your own lake and stream and supplying it with hand chosen organisms... but, if it's an open air system, don't be surprised if local organisms make their way into the system.

with a large enough shallow tank you could stand to catch a good deal of bug at night by hanging a small light above the surface of the water... bugs die, fish eat, fish poop, gammarus eat, plants grow... that's a pretty simplistic way to view it because there are a slew of microbes at work as well... but this idea could explain why the friendly aquaponics farm have been pushing the limits of a low density system...

they've been expanding their growing area and have only added minimum amounts of fish to their tanks... which means unless their fish have been constantly be over producing nutrients, that the nutrients to support the expansions are coming from somewhere other than the fish tank.

no one feeds the mosquito fish in the troughs, and yet their numbers continually grow... i'd be willing to make a wager that the amount of bio-mass provided via the mosquito fish and gammarus is fairly large portion of the total bio-mass of the system.

I'm not up on any research... just throwing this out there in case it's helpful.

You can set up a closed loop system that convert the sun's energy into edible food, but when you take that food out of the system it takes iron, calcium, etc. which are not derived from the sun. Instead something that already contains them (fish, fish food, banana peels, us) are broken down by bacteria and those minerals are made water soluble again, so plants can use them. Over time your plants will stop growing and your fish will die because of the lack of trace minerals. Even if you are feeding plants (duckweed for instance) to your fish, if you are eating any it's a net loss to your system unless you incorporate your waste back into it. The trick to minimal input and maximimum output I guess is to minimize losses of trace minerals and be as efficient as possible with the energy from the sun. The only other thing is to try to incorporate your own waste into system which opens up a huge (and smelly?) can of worms.

Agree.

Plus, Nitrogen seems to be locked in to a similar relation ship as trace minerals. The incorporation of sea salt could resolve some of the trace minerals, but unless growing plants that fix Nitrogen (a very small amount do this) there needs to be a Nitrogen source, IE fish food.

PS I have to much free time at work atm...

On the face Nitrogen seems different to me since my understanding is that some bacteria produce it as waste. I don't have time to study now though. Does anyone know the details of how Nitrogen (classified as a mineral?) is produced by bacteria?

Or do the bacteria eat everything but the nitrogen that's already in their food? Okay I don't know what the heck I'm talking about. Shutting up.

Nitrogen in as a gas in the atmosphere (N2) is very stable and unusable by all animals and most plants. It requires a process (Nitrogen Fixation) to turn into usable by plants/bacteria(most)/animals.

According to wiki http://en.wikipedia.org/wiki/Nitrogen_fixation, there are 2 natural ways: lighten and bacteria.

But when rereading it, looks likes some Azollas (kind of like duckweed) will fix nitrogen...

but your closed loop isn't a closed loop. if this system is out in the open, you're forgetting abuout the bugs and and what not getting into your system... heck, even dust particles carry trace elements in them.

to a certain extent a system will remain alive out in the wild as long as the water can remain oxygenated and flowing. now as to what extent the system is operating, that's up to the set up... if you increase the surface are of the fish tank while maintaining the same volume, you'll have a long and wide, shallow tank. no it won't be suitable for sustaining larger fish... but the smaller fish can live off of what naturally as driven to the water.

lakes and streams run like this... yes nature has plenty more things doing it's business into the system from outside the confines lakes and rivers... but if enough stuff naturally falls into the system, life can be sustained... and the best way to do this is to increase open water surface area.

bugs have blood, blood carries iron. leaves and other things that fall into the system will be consumed by the detritivores, and those detritivores also have blood that carries iron. this is how privately stocked ponds survive, so why not an aquaponic system?

now, in hawaii, there is a high amount of iron in the dust that floats around. i'd be willing to bet that in just the dust floating around in the atmosphere you'd be able to find what trace elements you'd need to sustain a system of a certain scale... it's just a matter of catching the stuff.

it sounds like a pipe dream... but really... no ones actually taken a look as to how to exploit nature to the fullest extent when it comes to ap... everything in AP is done by hand or manually introduced... and all i keep thinking about is, how do the mosquito fish and gammarus thrive when nothing is directly feeding them? yes the gammarus eats the solid fish poop from the fish that we feed... but the mosquito fish are carnivorous, and the gammarus are too big to fit in their mouths... so the mosquito fish have to be eating something else... something that's not manually being put into the system... and yes, in times of desperation the mosquito fish will turn to eating the plant matter... but there was never any damage to the roots of the plants... and considering the large population of mosquito fish in the system, if they had hit hard times when it came to their desired diet and turned on the roots, we'd have noticed the root damage and lack of plant growth...

There is no such thing as a system where you have zero inputs and continued outputs. If you have zero inputs then the system will last untill something is totally used up, then it fails.

There are many many posts here talking about feeding fish duckweed and BSL larvae and maggots and worms etc. But still inputs

unless a system is held in a clean room, or a vacuum, there is no way to eliminate all inputs to a system...

at any given second there is a barrage of matter at a microscopic level making it's way into the system. so unless you can find a way to keep these things from getting into the system, then the life in the system will persist.

yes, your big fish will die off due to malnutrition, but small things will still survive in the system by way of the available food sources... which find their way into the system naturally.

so again, unless you can prevent all matter from entering your AP system, some form of nutrition, whether it be in the form of bugs, or mineralized elements in the dust in the air, there will always be some form of input into the system.

playing on the semantics of "zero input" is an exercise in futility...

yes, some outside sources are necessary to provide the nutrition for the survival of the base food source, but i think the meaning of "zero input" really refers to the phrase "passive input" or inputs that occur naturally, like the build up of wastes or the breaking down of wastes into useable product... or food sources that make their way into the systems naturally...

the OP indicated that this system was to support plants and fish and humans. Any small amount of inputs that float in from the air are insignificant in this regard and would be totally unable to support the above.

superveg, you're right, when it comes to current system designs.

just because a system hasn't been built yet to support all 3 factors with passive inputs, that doesn't mean that it's not possible...

how about a raft system that pulls water from a pre-existing stand alone pond? a small pond that's been around for decades supporting the fish inside of it without direct feeding from people. pipe that water through a few troughs that raise vegetables. as long as your growing area output doesnt exceed the passive nutrient level input, then we're in business.

I see your point Damon and it's an interesting one. I think this pond we're speaking of that's been around for decades is around because no one's been fishing there and any plants that have grown in or around the pond have died and added nutrients back into the system. Pulling water out of the pond and into a growbed and eating the veggies grown here would drastically change the balance of the pond (unless it's a large pond and a small growbed, which I assume is much less practical than the OP wanted).

Hmm... I wonder if there's a good way to collect dust and incorporate it into a system. I wonder what level of trace minerals could be acquired? Also, there could be toxins and possible pathogens in dust too right?

You're right about the pathogens but again its already happening. Any increase in collection is also an increase in chance contamination. Its just weighing the pros and cons of doing do.

The the sustainability of the pond system would be determined by the size of the pond and the number of people its expected to feed. This is what the balance between the inputs and out puts would hinge on. Also. Removing the larger fish as to give the smaller fish a chance to grow and not be eaten would help the fish productivity...

I like the discussion you guys are having. The idea of a zero input system is not practical in any way. Simply the trace minerals would be depleted unless added in the form of sea salt, or a basic feed for fish (or human waste....)

It seems that fresh air would never be enough to operate an AP system, you would always need an input to keep the system running, be it bugs, fish food, or animal waste.

But,

How much of the mass in an Aquaponic system is related to the Co2 exchanged from the air? I think this % is quite large, and would appear an AP system could operate with a few selected inputs. Its hard to find what the Carbon content of a plants biomass is. I have done a few Google searches and come up empty handed.