System design

[Sylvia Bernstein]

What are your thoughts on system design?  Media vs raft.  Deep media beds vs shallow.  Siphons vs timers.  Tell us your thoughts and let's get the conversation rolling

[Murray Hallam]

So true TCLynx, the balance is important, if in doubt add more grow beds. It is not an issue at all if there are fish solids on the roots of any veggies grown in gravel especially flood and drain beds because fresh oxygen is being dragged down through the gravel every time there is a drain cycle. In a raft system the oxygen is much more critical because water cannot deliver to the roots anywhere near the amount of oxygen that air can.

TCLynx said:

talking about trying to filter solids with the lettuce roots so that you won't have to clean a grow bed. The truth is, if you have enough grow bed for the amount of fish you have, then you don't need to clean out media filled grow beds (that only happens if you are expecting a really small amount of gravel to filter a rather large amount of fish tank.)
Your lettuce will do far better if the roots are not all gunked up with solids. And if you add some composting worms into a grow bed, there should be no need to clean it out provided you are proving enough grow bed for your system.

[Shawn]

I guess I was thinking that the manifold pipe would essentially be a small growbed on its own. It's still flood and drain, so I was hoping that the sediment would still collect at the bottom of the pipe- if anywhere, and the roots will still get plenty of aeration on the drain cycle. The pipe will drain completely each cycle (no standing water) and the roots should still get plenty aeration. Thanks for the input though- I have reconsidered a thing or two, but I still feel it's worth a shot- worse case scenario is that the pipe gets clogged, or the lettuce dies. No big deal either way.

Murray Hallam said:

So true TCLynx, the balance is important, if in doubt add more grow beds. It is not an issue at all if there are fish solids on the roots of any veggies grown in gravel especially flood and drain beds because fresh oxygen is being dragged down through the gravel every time there is a drain cycle. In a raft system the oxygen is much more critical because water cannot deliver to the roots anywhere near the amount of oxygen that air can.

TCLynx said:

talking about trying to filter solids with the lettuce roots so that you won't have to clean a grow bed. The truth is, if you have enough grow bed for the amount of fish you have, then you don't need to clean out media filled grow beds (that only happens if you are expecting a really small amount of gravel to filter a rather large amount of fish tank.)
Your lettuce will do far better if the roots are not all gunked up with solids. And if you add some composting worms into a grow bed, there should be no need to clean it out provided you are proving enough grow bed for your system.

[Murray Hallam]

Hi TCLynx, I reckon your plan will work, go for it, see what happens. It is all good. On another note, most of us are tinkers. It is a lot of fun out of trying new things. I really enjoy that part of AP.

Shawn said:

I guess I was thinking that the manifold pipe would essentially be a small growbed on its own. It's still flood and drain, so I was hoping that the sediment would still collect at the bottom of the pipe- if anywhere, and the roots will still get plenty of aeration on the drain cycle. The pipe will drain completely each cycle (no standing water) and the roots should still get plenty aeration. Thanks for the input though- I have reconsidered a thing or two, but I still feel it's worth a shot- worse case scenario is that the pipe gets clogged, or the lettuce dies. No big deal either way.

Murray Hallam said:

So true TCLynx, the balance is important, if in doubt add more grow beds. It is not an issue at all if there are fish solids on the roots of any veggies grown in gravel especially flood and drain beds because fresh oxygen is being dragged down through the gravel every time there is a drain cycle. In a raft system the oxygen is much more critical because water cannot deliver to the roots anywhere near the amount of oxygen that air can.

TCLynx said:

talking about trying to filter solids with the lettuce roots so that you won't have to clean a grow bed. The truth is, if you have enough grow bed for the amount of fish you have, then you don't need to clean out media filled grow beds (that only happens if you are expecting a really small amount of gravel to filter a rather large amount of fish tank.)
Your lettuce will do far better if the roots are not all gunked up with solids. And if you add some composting worms into a grow bed, there should be no need to clean it out provided you are proving enough grow bed for your system.

[Sylvia Bernstein]

You are absolutely right about that, Shawn. Worth a few lettuce plants in the spirit of innovation. Let us know how it turns out!

Shawn said:

I guess I was thinking that the manifold pipe would essentially be a small growbed on its own. It's still flood and drain, so I was hoping that the sediment would still collect at the bottom of the pipe- if anywhere, and the roots will still get plenty of aeration on the drain cycle. The pipe will drain completely each cycle (no standing water) and the roots should still get plenty aeration. Thanks for the input though- I have reconsidered a thing or two, but I still feel it's worth a shot- worse case scenario is that the pipe gets clogged, or the lettuce dies. No big deal either way.

Murray Hallam said:

So true TCLynx, the balance is important, if in doubt add more grow beds. It is not an issue at all if there are fish solids on the roots of any veggies grown in gravel especially flood and drain beds because fresh oxygen is being dragged down through the gravel every time there is a drain cycle. In a raft system the oxygen is much more critical because water cannot deliver to the roots anywhere near the amount of oxygen that air can.

TCLynx said:

talking about trying to filter solids with the lettuce roots so that you won't have to clean a grow bed. The truth is, if you have enough grow bed for the amount of fish you have, then you don't need to clean out media filled grow beds (that only happens if you are expecting a really small amount of gravel to filter a rather large amount of fish tank.)
Your lettuce will do far better if the roots are not all gunked up with solids. And if you add some composting worms into a grow bed, there should be no need to clean it out provided you are proving enough grow bed for your system.

[Frank De Block-Burij (hygicell)]

Hi Murray,
Earlier on this thread I have posted some out of the box ideas on how to enhance aeration in a floating raft system by simulating ebb and flow
maybe you can comment on them?

Frank

[Alan]

Murray, Thanks for comments. I've received alot of help through this board. Now need to get started on something!!! We have New Year Holidays (Thailand) next month so have a few days to get it all up and running...

Murray Hallam said:

Hi Alan, I think the really big thing to come in high density food production will be the conversion of Hydro systems to Aquaponics. Hydro nutrients are skyrocketing in price and the bain of Hydro is pythium. Some industry insiders say that up to 20% of Hydro crops are lost due to pythium outbreaks.
The problem is almost non existant in Aquaponics.
The nutrient provided by the fish does supply all the elements needed to run a Hydro system and it does it organically

Alan said:

I've been following these boards with great interest. So firstly a big thanks you all for sharing so much info.
I've got a small barrel ponics system (Travis Hughey) working well but....I want to go commercial.
Before this interest in aquaponics I had a large hydroponic set up using NFT. Now in storage. So here I am with almost 2000 linear meters of NFT pipes, fittings etc and no source of information on how to convert toa continuous flow aquaponics system. Seems such a waste if I do not use all this stuff.
So questions,
1 Why so little info on NFT conversion? Any scientific reason(s)?
2 There seems to be loads on info on tank size to grow bed ratios etc. Is there some way to computer flow rates and nft runs per 1000 litre tanks etc.
Additonal info. I'm based in Thailand with had a warn climate all year round.
Plan on raising Tilapia and growing salads. I am thinking say 4 no 1000 litre tanks all connected (so I can harvest fish every 5 weeks or so). Set up a continuous 'flow' system.
Help me out here please.

[Murray Hallam]

Hi Frank, Sorry I am still learning to operate this forum software, so I can't locate your suggestion re aeration.
In floating raft it is very easy to add air stones to the trough. The example of UVI shows that it works best if air is added every 4 feet for the length of the grow trough. In my system I add very gentle flow of bubbles every three feet and it works well. Very simple to do.

Frank De Block-Burij said:

Hi Murray,
Earlier on this thread I have posted some out of the box ideas on how to enhance aeration in a floating raft system by simulating ebb and flow maybe you can comment on them? Frank

[RupertofOZ]

Murray Hallam said:

Hi Frank, Sorry I am still learning to operate this forum software, so I can't locate your suggestion re aeration.
In floating raft it is very easy to add air stones to the trough. The example of UVI shows that it works best if air is added every 4 feet for the length of the grow trough. In my system I add very gentle flow of bubbles every three feet and it works well. Very simple to do.

Frank De Block-Burij said:

Hi Murray,
Earlier on this thread I have posted some out of the box ideas on how to enhance aeration in a floating raft system by simulating ebb and flow maybe you can comment on them? Frank

Murray, Franks proposal is on page 2... and basically seems to be an idea that using a poontoon carrying either a styrofoam raft, or a gravel growbed... I couldn't quite grasp which.... the poontoon could be inflated to remove the plants from the undertank containing fish... then dunked back in periodically... a kind of "reverse" hydroponic style "ebb & flow"...

Frankly, other than a certain "echer-esque" appeal.... I just don't understand how such a method could either be cheaper, more efficient... or even overly successful... in comparison to either the UVI floating raft, or media based growbed styles of aquaponics...

I'll try and address the points directly Frank...

Frank De Block-Burij said:

1. why is it that in raft aquaponics fish are not grown under the rafts?
After all, there is where lies the biggest water body in the system.
Or in between rows of rafts, i.e. in long cages? This would keep the fish away from plant roots if that forms a problem, and make harvesting easy.
Fish densities overall would be much lower.
Even if the gravel would tend to clog, there are vacuum systems that allow the gravel to be cleaned, either directly in the water, or outside, in a filter system.
or an array of drainage pipes would allow to pump out most of the solids, (settling and floating) to a filter

The reason fish aren't grown under the rafts in the UVI style... or adaptations... is that the method is predicated on the removal of solids... and high oxygenation of the water.... to prevent root rot and pyrethrum... two common problems in hydroponics... (and the water in the rafts doesn't necessarily form the "biggest water body in the system"

As to the "gravel".. and "clogging"... sorry Frank, but I just don't understand your proposal in this regard...

2. rafts are used because they float, but the problem with them is they cover the water surface and impede oxygen exchange, this on the largest exchange surface in the system.
result: much more aeration needed, much higher energy consumption.
Easy to solve by using floats and grating to support the plants.
3. another problem with rafts is plant roots permanently in the water. It is one of the advantages of ebb and flow in grow beds
Solution: use hollow floats that keep the plants just above water level, i.e. standing on longintudinal racks.
These racks can serve as separation of the rows and form the sides of the long cages.
at regular intervals, pump air in the floats, the roots are lifted out of the water, are thoroughly aerated.
let the air escape, the roots are lowered and in turn aerate the water.
Ebb and flow turned upside down. Perfectly adjustable to different plant needs and stadia.
Cheapest would be long inflatable tubes.
hollow bottomed floats with solid sides would favourise oxygen exchange as the pressure on the air increases.

extra advantage of this system: a square tank is cheaper to build than a long narrow one

that's about it, for now
Frank

Yes, permanently submerging plants in water ... without sufficient aeration and removal of solids can indeed be problematical... as those that have tried to do so in DWC systems have usually found... but just as easily rectified ... again as most have found... by removal of solids and aerating the rafts...

The UVI model is the result of nearly 30 years of research and constant adaptation... and quite simply has been refined to work highly successfully in its current form...

In the raft style, ( as indeed even flood & drain)...there is an oxygen overhead for... the fish, and feed conversion... biological oxygen demand (BOD) for suspended matter, micro-organisms and bio-filtration... and plant root aeration...

The UVI model seperates and addresses all three oxygen demand stages individually...

In flood & drain media growbed systems... the opposite approach is undertaken... with all three oxygen demand stages... (primarily) addressed within flood & drain design...

To attempt to utilise fish underneath some sort of plant "structure" as you propose Frank... wouldn't address any of the three oxygen demands...

Unless you were prepared to highly oxygenate the underneath tank containing the fish...

The amount of aeration required however... IMO... would result in solids being constantly in suspension... and ultimately adhering to the plant root balls....

The additional requirement to "inflate" the pontoon to raise the plant structure...would seem to me to be just overly complicated... and even if the subsequent "deflation" were to aid in oxygenation of the underneath tank... probably not anymore efficient than just using a raft structure ... with aeration, and solids removal...

But, as I say... it has an "escher-esque" appeal... and might maybe work... at least partially... so build it Frank... and share your results with us....

To me... it just complicates both known working system styles... for no apparent real gains... and questionable "efficiencies"...

[Frank De Block-Burij (hygicell)]

Rupert, thank you for a tentative approach to studying my proposals with an open mind
and thank you for trying to visualise them
indeed, at first sight they seem to complicate things
but in my eyes, they really are a simplification:
with the exception of maybe a biofilter (and even that may not be necessary and/or can be integrated inside the raft tank), all external elements of the UVI system can be eliminated: no piping, less footprint, less hardware, very little appendages, lower energy consumption
this is obtained by making sure that "natural" oxygenation is enhanced in every possible way
in the first place by exposing the biggest possible water surface to air for the longest amount of time possible
in the second place by lifting the the plant roots out of the water, thus aerating them and by periodically dipping them in the water, thus aerating the water and feeding the plants, mainly according to the plants needs
but also adjustable to water oxygenation needs
we have discussed the extremely poor performance of bubble aeration and airlift pumps before on other forums:
as found and said (seconded by in depth research), it's performance depends on water depth and pressure difference and only starts to perform acceptably at depths of over 7 m, a situation not occurring in an aquaponics setup
it is easy to understand how the pressure differential and the travel time of a bubble through the water influences oxygen exchange
but this deeper pumping also leads to much higher demands on the blower, hence more energy consumption
whereas, if it were not for the rafts, a huge oxygen exchange surface lies at our disposition
so replacing the rafts by floats (these can simply be styrofoam plates suspended vertically in the water instead of horizontally on top of it) and a structure connecting two of them to support the plants would no doubt be a first improvement: much more water surface will be exposed to air, and the bacteria growing surface for nitrification would be doubled
eliminating the poorly performing diffusers will also avoid the solids to be kept in suspension as you rightly suggest: only the top layer of the water will be disturbed at intervals by the lifting and dipping
total average fish density would also be reduced:

and you know me: after careful thinking and pondering, I am ready to take up the (your) challenge, build the system and share the results
but it is in the thinking and pondering phase that I seek help:
maybe I overlook something
all my trials so far have led to positive results
with the exception of one: NFT
there rightly you have warned me of root clogging of the channels
I learned it the hard way
my conclusion:
NFT, unless you have oversized channels, is only suitable for fast harvested greens like lettuce
I know and appreciate your preference with sticking to known and proven setups
the wheel, the bicycle, the model T ford, and, more recent the computer, all took lots of time to develop
each of them were right and sufficient at their time
but would you imagine a world with only Commodore 64 computers, only model T fords or stone wheels?
we must continue to develop

Frank

Frank

[Murray Hallam]

Another problem in running fish under the rafts is that many fish species love to eat the roots.. Some folk run small aquarium type fish under the plants in the raft troughs for mosquito control

Frank De Block-Burij said:

Rupert, thank you for a tentative approach to studying my proposals with an open mind
and thank you for trying to visualise them
indeed, at first sight they seem to complicate things
but in my eyes, they really are a simplification:
with the exception of maybe a biofilter (and even that may not be necessary and/or can be integrated inside the raft tank), all external elements of the UVI system can be eliminated: no piping, less footprint, less hardware, very little appendages, lower energy consumption
this is obtained by making sure that "natural" oxygenation is enhanced in every possible way
in the first place by exposing the biggest possible water surface to air for the longest amount of time possible
in the second place by lifting the the plant roots out of the water, thus aerating them and by periodically dipping them in the water, thus aerating the water and feeding the plants, mainly according to the plants needs
but also adjustable to water oxygenation needs
we have discussed the extremely poor performance of bubble aeration and airlift pumps before on other forums:
as found and said (seconded by in depth research), it's performance depends on water depth and pressure difference and only starts to perform acceptably at depths of over 7 m, a situation not occurring in an aquaponics setup
it is easy to understand how the pressure differential and the travel time of a bubble through the water influences oxygen exchange
but this deeper pumping also leads to much higher demands on the blower, hence more energy consumption
whereas, if it were not for the rafts, a huge oxygen exchange surface lies at our disposition
so replacing the rafts by floats (these can simply be styrofoam plates suspended vertically in the water instead of horizontally on top of it) and a structure connecting two of them to support the plants would no doubt be a first improvement: much more water surface will be exposed to air, and the bacteria growing surface for nitrification would be doubled
eliminating the poorly performing diffusers will also avoid the solids to be kept in suspension as you rightly suggest: only the top layer of the water will be disturbed at intervals by the lifting and dipping
total average fish density would also be reduced:

and you know me: after careful thinking and pondering, I am ready to take up the (your) challenge, build the system and share the results
but it is in the thinking and pondering phase that I seek help:
maybe I overlook something
all my trials so far have led to positive results
with the exception of one: NFT
there rightly you have warned me of root clogging of the channels
I learned it the hard way
my conclusion:
NFT, unless you have oversized channels, is only suitable for fast harvested greens like lettuce
I know and appreciate your preference with sticking to known and proven setups
the wheel, the bicycle, the model T ford, and, more recent the computer, all took lots of time to develop
each of them were right and sufficient at their time
but would you imagine a world with only Commodore 64 computers, only model T fords or stone wheels?
we must continue to develop

Frank

Frank

[RupertofOZ]

Frank De Block-Burij said:

Rupert, thank you for a tentative approach to studying my proposals with an open mind
and thank you for trying to visualise them
indeed, at first sight they seem to complicate things
but in my eyes, they really are a simplification:
with the exception of maybe a biofilter (and even that may not be necessary and/or can be integrated inside the raft tank), all external elements of the UVI system can be eliminated: no piping, less footprint, less hardware, very little appendages, lower energy consumption
this is obtained by making sure that "natural" oxygenation is enhanced in every possible way
in the first place by exposing the biggest possible water surface to air for the longest amount of time possible
in the second place by lifting the the plant roots out of the water, thus aerating them and by periodically dipping them in the water, thus aerating the water and feeding the plants, mainly according to the plants needs
but also adjustable to water oxygenation needs
we have discussed the extremely poor performance of bubble aeration and airlift pumps before on other forums:
as found and said (seconded by in depth research), it's performance depends on water depth and pressure difference and only starts to perform acceptably at depths of over 7 m, a situation not occurring in an aquaponics setup
it is easy to understand how the pressure differential and the travel time of a bubble through the water influences oxygen exchange
but this deeper pumping also leads to much higher demands on the blower, hence more energy consumption
whereas, if it were not for the rafts, a huge oxygen exchange surface lies at our disposition
so replacing the rafts by floats (these can simply be styrofoam plates suspended vertically in the water instead of horizontally on top of it) and a structure connecting two of them to support the plants would no doubt be a first improvement: much more water surface will be exposed to air, and the bacteria growing surface for nitrification would be doubled
eliminating the poorly performing diffusers will also avoid the solids to be kept in suspension as you rightly suggest: only the top layer of the water will be disturbed at intervals by the lifting and dipping
total average fish density would also be reduced:

and you know me: after careful thinking and pondering, I am ready to take up the (your) challenge, build the system and share the results
but it is in the thinking and pondering phase that I seek help:
maybe I overlook something
all my trials so far have led to positive results
with the exception of one: NFT
there rightly you have warned me of root clogging of the channels
I learned it the hard way
my conclusion:
NFT, unless you have oversized channels, is only suitable for fast harvested greens like lettuce
I know and appreciate your preference with sticking to known and proven setups
the wheel, the bicycle, the model T ford, and, more recent the computer, all took lots of time to develop
each of them were right and sufficient at their time
but would you imagine a world with only Commodore 64 computers, only model T fords or stone wheels?
we must continue to develop

Frank

Frank

I'm sorry Frank... but (and I've said so before on other forums)... your basic assumptions are wrong... predicated on a belief that sheer movement of water alone in contact with the atmosphere...will acheive an oxygenation level that can sustain any more of a stocking density than that seen in natural systems.... way below what can be acheived in aerated aquaculture ponds, RAS operations, or aquaponics...

Now water movement... that is "agitated".... by weirs, waterfalls, rapids etc... will achive considerable more oxygen saturation than water merely "exposed" to air exchange, even if wind "rippled"....

But the stocking densities used, even moderately, in aquaponics... require as a minimum.... the "pull down" of oxygen through media filled growbeds by flood & drain... or in the case of UVI.... aeration of all seperated stages, including within the rafts...

There is no argument about the physics of water bubble contact/time in terms of oxygenation.... but the "deep" diffuses you refer to.... are actually highly "inefficient"... and seldom used....

Other than to turnover/lift oxygen depleted water from the depths you mention... to prevent stratification, and possible inversion... which can lead to 100% fish fatalities in a matter of minutes...

There is a physical, empirical limitation to the amount of oxygenation... hence stocking density... that can be acheived by normal air aeration....

And, even for extremely low oxygen species like Tilapia... the stocking densities sopmetimes quoted... of 100kg/1000L... are only acheivable by solids removal (which has its own aeration).... and pure oxygen injection...

Periodically dipping a raft of plants into a raft raceway... with no other aeration.... just isn't going to do it... at least not for the fish... without seperate solids removal... which you don't propose with your suggested "fish under raft" model...

Neither will their be sufficient bio-filtration... without solids removal/external bio-filtration...

There's no way, that you could match existing suggested aquaponic stocking densities... and keep your fish alive... in your suggested system... unless it was setup/fed by massive water turnover... ala trout raceways...

"Efficeint"... how long is a peice of string... and how much are you willing to pay for the peice of string... and how much time are prepared to invest...

Sorry Frank... but I'm calling it as I see it... based on all my knowledge and reading, particularly associated with my aquaculture course...

As I did with my suggestions regarding the adherance of solids to root balls in NFT... based on my experience in small scale commercial hydroponics...

You are welcome to doubt the advice... and prove it, one way or another, to yourself... but I wont endorse your system suggestion as "workable".... I believe it to be fundamentally flawed...

[RupertofOZ]

To be fair Frank... I have seen one implementation of your suggestions... not that involving a "dunking" pontoon apparatus...

But involving fish under and/or adjacent to plants on a series of interconnected floating "rafts"... that was producing an abundance of flowers... and could be called "aquaponics", perhaps in it's original "Incan" form...

But the fish (or in this case prawns) were virtually incidental... to the flower production... and stocked very lightly...

I'll dig up the video later tonight...