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GaryD

Aquaponics "Mythconceptions"

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Hi,

I've written a six-part series of blog posts that seek to debunk some of the fondly held notions about aquaponics. You can access the opening post....here.

Gary

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I not sure about Mythconceptions. When I started out they were general guidlines for the beginner, so they don't go out and buy 100 fish when there system had not cycled and even if matured could only handle 20 fish. Since I started I've run a system with a 9 to 1 ratio of water to media and have had 400 ish small fish in 380ltrs of water for months without loss. But I would still think a general guide line for beginners is a good idea. Poking holes may only lead to confusing the beginner. We can always push the envelope once we have the basics down.

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Hi Dufflight,

I not sure about Mythconceptions. When I started out they were general guidlines for the beginner, so they don't go out and buy 100 fish when there system had not cycled and even if matured could only handle 20 fish.

I guess that's my point. People are being told things like to buy 1 fish for each 10 litres of water capacity in their fish tank.....without regard for experience, species, or bio-filtration capacity. It's worth noting that one person who provides this advice has never succcessfully raised fish from fingerlings to dinner plate under this regime.

You and I can do it because we have sufficient experience to understand what's happening and we know what to do if our water quality monitoring starts to suggest a problem.

Since I started I've run a system with a 9 to 1 ratio of water to media and have had 400 ish small fish in 380ltrs of water for months without loss. But I would still think a general guide line for beginners is a good idea.

Interestingly, your system is seriously at odds with the general component ratio guideline of 1:2 (or 1:1) of fish tank to grow bed volume but it works because you know what you're doing.

In my view, we should be attempting to educate beginners properly rather than relying on such simple prescriptions.

We can always push the envelope once we have the basics down.

I totally agree. You and I both know more people who have killed fish than we do those who have successfully raised them to eating size and my contention is that they weren't properly educated in the first place.

Discussions like this one will help to address that problem. Thanks for your input.

Gary

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Hi,

It's my birthday so I saved my favourite bit of aquaponic nonsense for today. You can access "Mythconception #3 - Grow Bed Depth".....here.

Gary

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Hi,

And then there's the most ill-conceived and tragic of all of the mythconceptions "Mythconception #4 - Removal of Solid Wastes".......see here.

Gary

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As usual, now your making me think again... It hurts my head. Well, now I'm learning about mechanical filtration AND figuring out how to plumb it into the system.

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Hi,

Using just 10% of the water of conventional gardening and turning fish wastes into plant food, you'd swear that aquaponics was like mother's milk - beyond reproach......but it ain't necessarily so. You can access "Mythconception #5 - Sustainability"........here.

Gary

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Hi,

Last (in this six part series) but not least.....Mythconception #6 - Aquaponics is Easy!.......here.

Gary

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Hi,

The following is a response to comments received from Dr Wilson Lennard about a blog post that I made.

I've addressed the comments in this thread because the formatting features of the forum make it easier to do so.

Hi,

Just a comment about your article which does cite my name and an apparent argument I make for using the gravel bed in a backyard aquaponic system as a mineralisation filter. As always in media, when things are taken out of context or not completely included, then the argument required by the writer is supported. In this case, my name (and that of my close friends and collegues) has been used in the context of being an "advocate for leaving solids in backyard systems".

If you could spare the time to read the post again, you will see that I did not suggest you were an “advocate for leaving solids in backyard systems.” Quite the contrary. I was suggesting that you (like me) favoured the removal of solids from gravel systems.

What is sadly left out here is the fact that I also advocate that backyard systems are configured correctly in terms of fish to plant ratio's. If this was the case (which it isn't at all!; EVERY backyard aquaponic system I have ever seen, whether home built or purchased from a supplier, has the WRONG fish to plant ratio's employed - please note that I use "FISH to PLANT ratio", which is not "system volume ratios" or any similar erroneous ratio!) then we would have far fewer fish in systems than we do now, and then, the chance of "overwhelming" the gravel bed with solids would be far lower.

Since you’ve misread my original statements there’s little I can say except that I accept what you say about the “fish to plant ratio” as being logical enough.......and I share your concern about system volume ratios.

I read a statement in an article that you wrote which reads….

“Research conducted at Melbourne’s RMIT University suggests that, for 1 Kg of Murray Cod standing biomass, 20 – 25 Green Oak variety lettuce plants are required to balance system nitrate concentrations.”

Is this the sort of thing that you’re talking about?

I can see how the fish to plant ratio approach would be most useful in a commercial situation. Can it be easily applied to backyard aquaponics where there is likely to be a variety of different plants in a grow bed?

Anyway, your SYMBIOPONICStm approach sound interesting and I’d be interested to learn more.

The gravel bed WILL mineralise solids at acceptable rates without impacting on dissolved oxygen, biofiltration etc...in systems. BUT, if the amount of solids entering the system is too high (most likely due to the wrong fish to plant ratio being employed and the subsequent excess release of solid fish waste) then yes, the bed will be overwhelmed with solids. Therefore, gravel beds will mineralise solid fish wastes at acceptable rates IF the system is designed with the correct fish to plant ratio in mind. What happens mostly is that the fish to plant ratio is incorrect, so too many fish inhabit the system, and subsequently, too much solid waste enters the gravel bed.

I agree with you that gravel beds will mineralise solids. My central point is that they will function even more effectively if the solids are removed and processed externally – with the nutrients being added back into the system.

In addition, I have NEVER said "...up to 75% of the solids in an aquaponics system may be in solution." What I have said is that up to 75% of the wastes produced by the fish in the system are in the dissolved form, because they dissolve directly into the water across the fish gills, OR, up to 75% of the nutrients in the water are in dissolved form. This may seem a trivial reading of what you have said, and it may even seem pedantic. BUT, the fact is that the statement "...up to 75% of the solids in an aquaponics system may be in solution." is completely factually different from what I have ever said!

You were correct – I misunderstood what you wrote. On reviewing the source of the material I can see that I interpreted the term “waste” as being solids rather than applying to all waste (including ammonia emanating from the gills) coming from the fish.

I don’t believe that your concern is trivial or pedantic – and, while it doesn’t alter my main contention, I’m entirely comfortable with you pointing out the error of fact.

So, I am not against the information you are supplying to the public; much of what you have to say seems based in reality and uses common sense. In addition, there is much (but not ALL) that I agree with.

I’d be happy for you to speak about those specific things that feel you cannot agree with.

However, if using peoples names to make arguments, it would be nice to stay true to that persons beliefs and NOT to use that persons name, and more importantly, your interpretation of what they may have said, as an argument to support your own thoughts or feelings.

As I’ve already pointed out, your original concern is the consequence of your misreading what I wrote…….and I’ve addressed the error of fact. If you have further concerns, I’d be happy to hear about them.

Thanks for your time,

Thank you for your time. I hope that my response does something to address your concerns and that you feel inclined to let us know more about how SYMBIOPONICS works.

Gary Donaldson

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Hi,

On 10th November, BYAP's Joel Malcolm made a post on a thread called Solids removal - how and why?

This was a significant post and is worthy of further scrutiny.....

I don't remove solids from my systems, except for the large floating raft system where the larger solid matter is broken down outside of the main water flow. If you're having troubles with solid build up in your beds then you have too many fish, or preferably not enough beds and as such plants.

No suprises there......Joel is a fundamentalist when it comes to flood and drain grow beds. I'm sure he wouldn't be too offended if I said that he liked the simplicity of the standard recirculating Speraneo-style aquaponics system and he's promoted its use for some years now.

I do think Joel is a bit limited in his assessment of the options. If you're having trouble with solids you can also remove them and/or consider an open loop plant growing regime that can accommodate water with a high solids loading.

One of the biggest input expenses for a system is fish feed, one of the biggest outputs from a system are the plant crops.

Yep......most people would agree with that.

By my way of thinking you're better keeping the fish stocking levels lower and making complete use of the feed going into the system, as well as the wastes from the fish.

This is the interesting bit. This is not the first time that Joel has referred to low stocking densities as being the secret to making a standard flood and drain aquaponics system work.

In fact, I'd go so far as to say that it's the only way that they can be made to work......and that assumes a 2:1 (or greater) grow bed to fish tank volume, plenty of aeration and a fish species that is not too fussy about water quality.

If you're chasing high stocking levels of fish, then to push your levels higher you will need to remove solids, and this brings about complications, inefficiencies and more work.

The need to remove solids for anything other than low stocking levels is pretty much what I've been saying from day one. It's interesting to see that Joel is now starting to take a similar line.

Where Joel and I might part company on this one, however, is the bit about "complications, inefficiencies and more work."

Good system design will address the solids problem and you'll end up with an aquaponics unit which is far more efficient than a standard system.....and you'll be handsomely rewarded for any small additional effort with more fish, healthier plants and a more cost effective operation.

For my money I'd go with less fish and no solids removals every time. I know that some people love to have lots of fish, but I'm happier to go with a simpler balance.

If you're not concerned about getting a return on your investment in your system (assuming you laid out the big bucks that it takes to put a reasonable - 2,000+ litre fish tank/four to six grow bed - kit system)......or you managed to cobble your system together out of recycled components for little outlay......you may also choose to go the "simple" route.

Even then, your power bill may make those vegetables and a few fish pretty expensive by the time they get to your plate. Remember, it costs the same to pump water regardless of whether the fish tank has no fish or many fish.

If your main game is growing organic vegetables, there are much surer and cheaper ways of doing it than running an a lightly-stocked aquaponics system.

Gary

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This is still an Aquaponics Forum. Or did it change to a diss AP or people in AP at any chance. If so I didn't get the memo. And a forum name change is in order.:confused:

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Hi,

I'm not sure how you arrived at the "diss" (what is that anyway?) bit about AP or people.

What this forum is about is discussing ideas related to food production. It's not essential that people agree with each other. In fact, in the interests of objectivity and advancing the discipline of aquaponics, it's a good thing that people challenge ideas.

As I demonstrated through my "mythconceptions" blog posts, there are good reasons for closer scrutiny of some of the ideas that attend aquaponics.

I've spent some years challenging some of the fondly held (but fundamentally flawed) ideas about things like solids removal and grow bed depth, and it seems that a different view of the world of aquaponics is finally beginning to gain traction.

While most people to whom I talk seem comfortable with that, all it seems to have produced from the architects of some of the mythconceptions (or their sycophants) are personalised rants.

There are no secret cows on this forum......and, unlike some other forums, no-one gets bullied or locked out of here for taking a contrary point of view on any aquaponics or food production-related issue.

Got anything technical to contribute to the discussion?

Gary

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Its the fundamentally flawed bit. Most of these Mythconceptions you are talking about are general rules for beginners to help minimize the failure rate of new systems. Bit like training wheels or speed limits for learner drivers. We can all push the boundaries once we have a firm grip on AP but I don't think its wise to throw a kid on a bike for the first time without help or to tell a learner driver to go as fast as they like. I don't think telling beginers to use shallow GB's is a good idea. When they have trouble growing things or are under filtered we will have to tell them to add more media. But if they have allready cut there GB's to a lower height we will have to tell them to get new ones. And there is still no working model to base this on any way.

And diss is a short version of disrespect. This is the only forum to my knowledge to have a PHD politely tell them to stop using there name.

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Hi,

This is the only forum to my knowledge to have a PHD politely tell them to stop using there name.

While that's not quite how it happened, is it possible that this is the only forum that is capable of capturing the attention of someone with that sort of background?

In allowing yourself to be used to fire other people's bullets, I hope you're taking the time to reflect on the irony that this is the only forum that would allow for that. I keep reminding myself that, while you are provocative (in a personal sense), you are acting at the behest of others who would like to do what you do but lack the courage.

Have you thought of anything new of a technical nature to bring to the discussion?

Gary

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Other people's bullets. These are my views and I don't speak on anyones behalf but myself.

Nothing new of a technical nature until new toys get here.

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Nothing new of a technical nature until new toys get here.

Love toys......what's on your list?

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2x JVP-102B 5000lph For the inside tank, but will put them in the swirl filter first to see what happens with 10000lph water pump and 2x 5000lph jets do.:D

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Hi,

As Castaway evidenced in his (faintly hysterical) comment on my blog post Mythconception #6 – Aquaponics is Easy, not everyone is comfortable with my suggestion that it might not be as easy as some people have been told……or have been telling other people.

BYAP contributor TCLynx has gathered several of the more commonly held notions about aquaponics together in (what I suspect is) an attempt to make sense of the “guidelines” (read Mythconceptions).

While I commend her for her efforts to make aquaponics more understandable, her post illustrates the difficulty in attempting to formularise aquaponics.

MAX fish stocking per minimum grow bed/fish tank volumes

3 kg of fish per 100 liters of flood and drain media filled grow beds with 50-100 liters of fish tank

(1 lb of fish per 5 gallons of flood and drain media filled grow beds with 2.5-5 gallons of fish tank)

My experience suggests that the stocking rate is dependent upon water quality, and that is influenced by many things. It is simply not correct to say that you can load 3kg of any fish species into 50 - 100 litres of water serviced by grow beds with a capacity of 100 litres.

At the low end, that may mean that you have a stocking rate of 6kg per 100 litres (based on the 3kg at 50 litres). While you might be able to keep certain species at that level, you certainly couldn’t keep others at that rate for very long.

Ratios

When we talk about ratios it is grow bed to fish tank. A 2:1 ratio means there is twice as much grow bed volume as fish tank. Yes, if you have twice as much grow bed as you have fish tank, you then need a sump tank or some other means to keep from running the fish tank dry.

While this is a common generalization, it may not be sustainable in certain situations….particularly at a stocking rate of up to 6kg per 100 litres.

Pumping

Pump the volume of your fish tank each hour (if pump is running on a timer, pump should move the volume of the fish tank in whatever fraction of an hour it is turned on.)

Once again, the required turnover rate for the water in the fish tank is driven by the particular circumstances of a given system……and that may mean that the water might need to be turned over more (or less) frequently.

Aeration

Though flood and drain grow beds provide all the aeration that the plants and bacteria needs, it is good to have supplemental aeration for the fish tanks even if it is not strictly needed to keep the dissolved oxygen up for the fish, the extra circulation provided by the aeration can help keep fish tanks cleaner. Also having a supplemental air pump can make it easy to hook it up for battery backup in case of power failure.

-1 cfm (cubic foot per minute) at 2 psi (pounds per square inch) for 400 gallons of fish tank.-

?aprox 18 liters per minute at 13 kPa for 1000 liters of fish tank

I agree with TCLynx’ general proposition of having plenty of air in the system.

Grow bed Depth

A relatively standard depth for grow beds is 30 cm or 12 inches. This seems to be a good minimum depth that provides plenty of dark space for bacteria, solids filtration, and root depth while still allowing for dry media on top and when using siphons, constantly flooded media at the bottom. It is possible to use shallower beds but they have greater challenges. Deeper beds are definitely functional though they provide less planting surface for the same amount of gravel. Deep beds are a good choice for those wishing to place DWC or NFT growing space after the deep grow beds.

All of the attributes TCLynx states for 300mm grow beds hold true for shallower ones, too. The challenges to which she refers are minimal and the benefits of using shallower beds (depending on the circumstances) may be significant.

Solids removal

Highly debated topic

If plenty of flood and drain media beds are used, solids removal is not needed.

However, if trying to grow lots of fish with minimal filtration, then the added complexity and labor of solids removal becomes necessary.

What does plenty of flood and drain grow beds mean? What does lots of fish mean? As I’ve already demonstrated, taking TCLynx' assertion that you can keep 3kg of fish in 50 litres of water (equal to 6kg in 100 litres) could be a potentially catastrophic prescription in itself.

As I’ve already pointed out many times, grow beds are bio-filters and heavy solids loadings will impair the performance of bio-filters.

So, we come back to the point that it is simply not possible to generalise around aquaponics.

The problem, as I see it, is that some people are unable to grasp the simple fact that aquaponics is not as simple as they would like it to be. Others understand this, but obviously feel that it is not in their interests to have people believe that aquaponics may have its own (sometimes protracted) learning path.

As someone with a broad interest in backyard food production that spans 30+ years, that realisation neither surprises nor dismays me.

I’m used to the fact that each food production discipline…..be it chickens, quail, vegetables, snails, cattle, fruit trees, sheep, goats, grains, aquaculture, rabbits, herbs, fungi, hydroponics……has its own body of associated knowledge and skills that have to be learned and mastered for successful consistent production to occur.

Let’s take poultry production as an example. If we were to take an aquaponics is easy approach to poultry production, we might say that poultry:

  • produce 200 eggs per year
  • take 19 days to hatch
  • need to be kept at a temperature of 28 degrees C
  • feed should be about 19% protein
  • grow to 1.5kg in 60 days.

When we get into the detail of poultry production, we discover that:

  • some species of poultry produce up to 300 eggs per year while some obscure species of geese struggle to produce 20 eggs per year.
  • Chicken eggs take 21 days to hatch while those of Muscovies take 35 days.
  • Day old chicks/ducklings/poults need to be kept at around 35 degrees C while adults can (depending on the circumstances) sustain anything from below freezing to 40+ degrees.
  • Broiler chicks will require feed with a protein level of 22+% while laying pullets will require something like 17%.
  • Broiler chickens will grow to processing age in 35 days while a goose may take six months.

If you were to apply the simplistic formula that I described earlier, you would have dead birds everywhere…..and a stinking mess to boot.

So why would we expect aquaponics to be any different?

-o0o-

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Hi,

For those who may be interested......you can see my latest blog post "Mythconception #7 - Grow Tank Depth".....here.

Gary

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Only thing I see is one is talking Hydro and the other side is AP. Shallow may work well with both but I would think the temp would be more stable with a greater depth. Fish wise I like the more stable enviroment. There are also a lot of mtr + ones with the fish under the rafts. This way the fish keep a lot of solids from settling on the bottom. The roots I expect must be protected.

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I can understand the reasons for growbed depth of 300mm, but I see no reason why 300mm floating raft troughs would be any better than 200mm. If the parameters are the same in each trough, ie flow rate, airation, nutriet levels etc, I would strongly doubt any difference could be seen between 2 troughs of different depths. As for temp stability etc, most rafts are polystyrene, and with the flowing water etc, I doubt the shallower ones would get any more or less temp fluctuations. I haven't seen anyopne actually claim 300mm troughs are neccessary, but I assume they have somewhere (links please)

Damo

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