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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

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Murray and Rupert,
I m' sorry to have to remark that you still don't see the whole picture
as in my original post I believe I covered all your objections:
the fish do not actually have to be under the growbeds, Murray:
"Or in between rows of rafts, i.e. in long cages" is what I wrote
still the fish would benefit of the large body of water
which automatically means that actual density is lowered far beneath that of a separate fishtank, nearing that of nature as you suggest, Rupert, so "natural" oxygen exchange might very well do
besides I do not exclude agitation if that should be needed
I even include it:
the dipping of plant roots will agitate and oxigenate the water, the dripping of water droplets from the roots when lifted up will agitate the water whilst the roots are aerated.
In the aspect of aeration my suggestion is not very different from a growbed ebb and flow system, might even be more efficient.
"or an array of drainage pipes would allow to pump out most of the solids, (settling and floating) to a filter" is what I wrote
this pumping too will agitate the water
using gutters instead of pipes will further aerate the water
putting some obstructions (i.e. pebbles), cascades, even a flow operated rotating brush in the gutters will disturb the flow, prevent it from becoming laminated: lots more aeration, all very simple to imply
all this with a pumping head limited to say 30 cm or less

and all these extra surfaces can and will be colonised by nitrifying bacteria

I am not going to engage in another yes/no discussion on the efficiency of bubble aeration,
been there, done that, not doing it again
I provided you with the scientific papers that led to my conclusions, lots of them
still you continue to question this without backing it up

Would like to see the video, even if it doesn't incorporate the "dunking pontoon" which is the core of my suggestion
friendly greetings
frank
Yep, Frank.... you could construct adjoining raceways/tanks for the fish,install extra piping to remove solids (how???)....

You could install baffles, freeforms, pebble rapids, spillwaters, gutters (unconvinced).. even a couple of hamsters turning paddle wheels....

But for what reason... at best, to acheive a level of oxygenation that can/is acheived by existing methods.... to acheive stocking densities either slightly above a natural system... or comparable to exisiting densities acheived by existing methods...

And all sorts of levels of complexity, and management....

But for what...

Most people have small backyard flood & drain systems... aerated by the flood & drain action... usually supplemented by a 4w, two outlet air pump.... possibly even incorporating a couple of small rafts... either in a raft bed, or even floating on the tank/sump.... without any problems...

Commercial scale systems like the UVI model... often employed in warm/hot climates.... aerate the seperate stages... usually from a single centralised distribution point/blower... without any problems...

Both with a minimum of maintenance requirement... and/or level of operator training....

Both systems maximise the removal of nitrates... and conversion to plant growth.... while avoiding many of the problems of root rot, root drying, channeling, water temperature control etc... found in traditional hydroponics...

And acheiving levels of bio-filtration and oxygenation effective and comparable to those in RAS aquaculture...

I just don't see that introducing a level of complexity, cost, and management... justifies... what benefits???....

Dunking the roots of the plants... for an unknown duration... via an unknown periodic cycle... for unknown results of nitrate removal/uptake... for unknown growth rates... with unknown oxygenation returns... with possible water temperature rises/oxygen depletion through periodically exposed shallow raft beds... exposing plant roots to heat for unknown periods... possible algael growth through sunligh exposure....

For unknown benefits.... and unknown costs... for unknown reasons... other than perhaps a degree of intellectual satisfaction....

Build it Frank.... and report it ... honestly....

So far, on numerous forums and other aquaponics groups, you have postulated various things... and ultimately, after alienating many participants and despite being challenged to "prove your theories"....

You have never, even on your own website.. other than some photos of greenhouse construction (apparantly now defunct)...actually pictured/documented/reported a single growing plant... or successful fish growout...

To coin a phrase Frank.... "Show me the money..." ... or in this case.... "Show me the system..."

Time to money up and have the courage of your convictions Frank.... if it works... I'll happily tip my hat to you...
Oh, by the way... using compressed air to raise pontoon type floats.. thus the actual rafts... might actually be benficial in terms of harvesting/planting... and I'm sure that it's probably been done.... or will be done... by someone who is prepared to invest the money for whatever percieved benefits...
the usual replies, Rupert
I am not surprised
frank
Here's the video I promised... note the water circulation (and aeration) by a 1/4 hp pump at the opening of the video... and note (you'll have to research).... the stocking densities of the "shrimp" employed....

And note... the unincumbered simplicity of the system...

Not really different ... to floating some rafts, with perhaps water chestnuts... in a tank/pond/pool... just a slightly bigger scale...

http://www.youtube.com/watch?v=c2z-IdnIGLE&feature=channel
This is quite a discussion to wake up to. At this point, Frank and RupertofOz I'm afraid I'm going to need to jump in here, play referee, and ask that you take what appears to be a topic with a long, emotional history across several other forums somewhere else (i.e. email or a different forum) unless there is something new to discuss. Thanks
Noted, I'm done on this topic Sylvia... there's nothing further to be gained from continuation..
thanks for the video, Rupe
very enlightening,
wading in the plant growing area is what I was thinking of
no reference to shrimp density though, so some research is indeed in order
seems like the open surface is sufficient for "natural" oxygenation
so my idea of parallel plant and fish space in the same water body might very well work
and the lifting and dipping contraptions might show to be unnecessary
a real step forward towards simplification
so thanks again

and thank you for your intervention, Sylvia
though to me quite unnecessary:
I was ready to retire from the discussion like I previously did for three weeks
as I do not wish to disturb your forum, I have exchanged private mails with you on the subject

Rupe and I have known each other for a while now
we are conscious of our differences
still I consider him as a much valued friend
wish he would be ready to step out of the box every now and then, though
and maybe I might be accused of pushing a little to hard
but that is inherent to enthousiasm
so forgive me for it

I am convinced that what I brought forward is new
so belongs here, right on this thread

frank
Thanks for your understanding, guys. Sorry if I seemed heavy-handed. You are both brilliant aquaponists, and I'd love to draw you into some other topics. For example....I'm pretty intrigued by the vertical stacking system that Cosmo has posted some great photos of. I purchased a vertical stacker last summer to play with aquaponically, but never got to it. What are your thoughts?
a subject I admit not knowing anything about, Sylvia
but I took along the existence of it in the background of my design
it is one of the reasons I am pretty self assured that it will work:
if dripping down aquaponic water over plant roots is succesful
then dipping these roots in aquaponic water must have the same results
after all, the plants don't know nor do they care where the nutrient rich water comes from

frank
Frank De Block-Burij said:
if dripping down aquaponic water over plant roots is succesful
then dipping these roots in aquaponic water must have the same results
after all, the plants don't know nor do they care where the nutrient rich water comes from

frank

There is a definite distinction though Frank... between plant roots being continuosly moist & fed by nitrient rich water... by continous drip, or a continous thin film...

As opposed to "dipping" them intermittantly into nutrient rich water... and then exposing them for a period of drying in air...

It may well indeed work, but would probably involve considerable trial and error to determine the necessary period of immersion, and frequency of immersion.... for satisfactory nutrient uptake/plant growth...

And to determine the safe period of air exposure, and seasonal/temperature variations... to prevent the roots drying out..
Like in nature, Rupert, I believe this to have a very large margin:
as long as the roots are not allowed to dry out thedanger is minimal
it is well known that tomato roots can be trained to find their food deeper in the bottom
like with people:
what doesn't kill you makes you stonger
frank

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