Backyard Aquaponics
A place to discuss aquaponics

Hi,

I've seen interest around this question mounting with recent posts by njh and RupertofOz. I've also referred to run-to-waste (open loop) systems in previous posts.

For what it's worth, this is my view.

Does an aquaponic system have to be recirculating (closed loop)?

Not necessarily.

Do the plants have to be grown in a closed loop?

No. You can grow plants in a run-to-waste system just as effective as you can in a recirculating system.



I wonder what the evidence is for such an observation.



As I've pointed out in previous posts, the term "run-to-waste" ought not imply that much water is wasted. Using coco peat as an example, run-to-waste system are usually set up so that about 10% of the daily feed regime is wasted. In practice, even this small amount can be collected and used to feed other plants.

As njh pointed out.......



You can read about a very simple system that is non-recirculating..... http://www.cityfarmer.org/fishfarm.html



......and now we arrive at a major reason why most of do whatever it is that we do......because it's what we prefer.

While I am not in favour of open loop as such - I do intend to remove a portion of the water from my system every week which I will use to water conventional gardens (eg my raised bed veggie gardens). The water that I would otherwise have used to water the garden will go into the aquaponics system instead (from rainwater tank) to replenish what I have used in the watering process. The advantages of this as I see it include:

1. The conventional garden will receive the benefit of the nitrates
2. I can run higher stocking levels in the aqua system and vary the use of the water from the aqua to suit the density of fish and/or plants I have in my system at the time
3. By not having the system entirely closed I will be reducing the risk of accumulation of bad stuff that may be in feeds or leach from pipes etc I am using in the system.

I guess this is another variation on the theme - one which I see as having few disadvantages. The only ones I can think of are:

1. Potential for fluctuations in PH and temp when doing the changes. In this regard the changes should be kept to be a small % of the system and could be done in lower % but a couple of times a week.
2. Loss of some valuable component of the ecosystem. I think this would not be the case given the small % replaced at any time.

Agreed Gd that "open loop" seems to have advatages of simplicity and possibly costs relating to power, purchase of system components etc, an issue that has been occupying some of my thoughts.

Yep I like the "closed" nature of AP due to it's inherent balance and self-sustainability, or at least fairly close to.

Is it or does it have to be the only ... hell no, and for some of the reasons above it certainly isn't perfect.

Not in any way knocking anyone or any other approach or alternatives.

Re : "Run to waste".... I'm inherently biased as to both the wastefulness and the potential pollutants from "traditional" systems especially hydro....

However hydro production is and has been for many years a proven method of obtaining high return for minimal investment (depending on scale etc etc) and from what I've seen so far AP (as yet) doesn't appear to match either yield, consistancy of yield, or cost/price comparisons to a hydro setup.

Does that mean I wont persue AP.... definitely no... I really believe that ultimately an adaption of some hydro techniques and equipment with AP to supply the nutrients is exactly the sort of "closed loop" system that appeals to me.

As you say, in many ways in the end that's probably what it comes down to.

I'd hate to live a life blinded to other ideas though.... and thank goodness for forums like this I say.

Woo Hoo! Glad to hear it!

Garry - I am not sure I am clear on the type of open loop system you refer to, but I wonder whether it would sustain as many fish and plants as the closed loop system where plants continually have access to any nutrient they desire and therefore nutrient removal and plant growth is theoretically optimised. Can you explain your proposed method in terms of this comment so I can better picture it.

GD, is it" because its what we prefer "OR is it what we know.
So far a major percentage of people(I think) have been in the closed loop systems for one reason or another, but as the interest grows in open loop systems more and more will experiment and ideas will float around.But until we know more about how it works eg advantages/disadvantages, its hard to leave what we know.Not everyone has the pioneering spirit which is why I joined the forum,I may be good at one aspect of AP but crap at others,so I learn,input what i have and take what i need.
If the open loop system (in your opinion) is a good way to go keep up the discussions and I`m sure the method will be adopted in time by others here.

For sure...

I mean for example these our friend at the Scottish Institute who's been running an open loop system but is looking to maybe include some AP ideas and several others that run open systems with flowing ponds/reeds etc.

It's all about the ideas and differences that make this such a great place.

I reckon I've reappraised/tinkered/fine tuned my system design sevral times as I've read throught the posts here and I hope that continues to happen.

Not totally opposed to open loop at all.... previously I'd utilised the tank for grey water recycling via drip feed to a soil garden and occassional flood to a couple of fruiot trees.

Will definitely incorporate an overflow system into my design to cater for heavy rain and/or water change outs, quarantine procedures etc.... and that'll all go back to the garden or fruit trees.

Maybe we should distinguish closed loop, semi-closed loop, and open loop.

The terminology seems to indicate that closed loop you put in fish food & top-ups, you get out fish, and veggies. Semi-closed is the same, but you turn over the water in your system to feed other plants, etc. Open loop would seem to indicate that the input water doesn't get used twice, such as a flow-through aquaculture system.

I would tend to like the semi-closed, since that helps erradicate salt buildup, it would also reduce the accumulation of heavy metals, etc.

Hi Greneedo,

My understanding of aquaponics is that it is a combination of aquaculture and hydroponics......in fact, the original term for aquaponics was Integrated Aquaculture. I've never seen an aquaponics system which did not feature hydroponics as part of its make up.

If you accept this definition, then any combination of aquaculture and hydroponics is aquaponics. There's no automatic connection between aquaponics and recirculation.

When I use the term "open loop" I'm not suggesting that we discard the water. In its simplest form, an open loop (I prefer the less confusing term "non-recirculating") system involves taking the water from the fish tank and using it to water plants in any one of several hydroponic growing systems. Any problems associated with salt build up are sorted by periodic flushing of the system with fresh water (rain tends to do this automatically).

Please note.......I'm not suggesting that I don't like recirculating systems ...or that they do not have distinct advantantages of their own (I have both types)......simply that recirculating systems are not the only option.

Some of the comments that I read suggest that there is some distinction between hydroponics and the growing systems used in aquaponics. The fact is that they are one in the same. As I said previously, I've never seen any growing system in aquaponics that I haven't previously seen used in hydroponics.

The only distinction is how we source the nutrients. In AP, we get the nutrients from fish while in hydroponics we source the nutrients in any one a variety of ways - including organic options including fish waste.

VB - as for how much one system produces compared to another, that's a question of management.

I was of the belief that the best hydroponic systems would outproduce aquaponics.......largely because of the ability to more accurately control all of the parameters......but there are others who believe differently.

The same thing applies to aquaculture.......commercial aquaculture systems have a much higher ratio of kilograms of fish to litres of water than most aquaponic systems.....but they do so at a financial and environmental cost.

In either case, I'm able to be persuaded otherwise.....but by evidence rather than anecdote.

Gary- I was just trying to clarify a little that the semantics of "Open" versus "closed" can be somewhat confusing. I only used the example of flow-through aquaculture to distinguish between a completely "open" system versus a completely closed or recirculating system.

I agree that both aquaculture and hydroponics can produce more of their product per volume or area, the problem that each of them have is excess waste of one sort or other. The combination of the two into aquaponics tends to reduce waste since one system's waste is what is often supplemented in the other.
One of my interests in Aquaponics is due to my problems in the past with hydro. Overdoing the nutes in Hydro burns the plant. Fish, on the other hand are something I have done for nearly 20 years, and I can understand that. I was nearly resigned to give up on hydro, and stay with aquariums and dirt gardens, when I happened upon the Aquaponics.
I don't pretend to have anyplace close to all the answers, and you are much more successful in hydro than I.
I was just seeing some apparent confusion about semantics of recirculating, non-recirculating, and somewhere in between systems.

A significant advantage of 'open loop' (which, as I said on my blog, is a poor name) is that you can add unfish safe chemicals between the fish and the plants. For example, you might boost P levels every now and then with some soluble P, or add lots of iron to kill off slugs.

Bzzzzzzzz, sorry guys, the hydroponic side of an aquaponics system has been found to exceed normal inorganic hydroponic production.. In fact not only just exceed normal inorganic hydroponic production, but for many plant species aquaponic plant production can be up to double the equivalent hydroponic production.

Dr Nick Savidov has carried out trial for many years comparing plant growth rate and production levels between the two, and a 'mature' aquaponic system far excedes the yields of normal hydroponics.

Anyone who attended the workshops in August last year will have seen the photos and heard all about Dr Savidovs trials. He even told us about how he felt there was some problems with nutrient level variations in his trials. So he analysed the aquaponic water for all of it's maco and micro nutrients, then created an inorganic nutrient solution with exactly the same levels of nutrients for a growth comparison. Aquaponics still far exceded the growth rates of the conventional hydroponics..

http://www.aquaponicsjournal.com/articl ... perior.htm

But this may be getting a little off topic...

I'm not sure I could agree with this statement though about water consumption made previously:

earthbound: yes, I would expect AP to out perform inorganic hydroponics, and indeed I appraoched AP from the direction of wanting a reliable supply of fish poo nutrients rather than for growing fish. Others I know also have found better growth from fish poo.

To be clear, I think people are using the terms hydro and aquaponics with different meanings (and of course misunderstanding each other as a result). Perhaps we need a glossary?

re my statement about open loop using less, it is based on the observation that open loop systems move less water around and thus have less opportunity for evaporation. Other people (such as autopot) have quantitative evidence that it is true. Perhaps you can give reasons why you don't agree with this? (And how much water is used to make the extra power to move the water around?)

Yeah, it can be tricky when AP is partly hydroponics, that is why I have tried to discern by saying "inorganic' hydroponics...

I'm not sure I understand how moving water around creates more evaporation. I found their website but haven't found much about evaporation on there as yet, do you have a link njh? So far as control mechanisms, the systems I have can't be much simpler, most of them have no control, but yes they do have pumps, the fish need em...

I like this loose definition, as long as we make the point that run-to-waste does not mean water is going down the drain.

I'd be happy to add thse definitions to the glossary alond with any others .

Njh, you had a few you wanted to be put in?

Steve