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PostPosted: Dec 31st, '08, 18:45 
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RupertofOZ wrote:
hygicell wrote:
TCLynx wrote:
I think it would be about 3kg of fish per 100 l of grow bed.

there is discussion on this issue
TMHO fish density is related to recirculation rate
and should not be expressed in kg/m³ but in kg/m³/hr
frank

Only partially Frank... ultimately it's more related to filtration capacity.... which in itself can be influenced by... or limited by flow rate...
The figure given and repeated is a "safe" density ... and an easily calculated guide...
Most people wouldn't probably be able to measure there flow rate anyway....
And stocking at the suggested density with the style of media based growbeds has been demonstrated to work ... consistently.... over and over again .... for everyone....
With experience, and or alternative equipment... higher densities are acheivable.... with correspondingly greater costs, time/monitoring involvement and greater risks....
We're talking backyard aquaponic systems.... not high intensity RAS systems... or commercial scale operations....
IMO... floating raft.... and pre-filtered delivery to NFT.... may scale better to commercial reality than growbed systems....
But involve adoption of auxillary equipment... and can be limiting to what vegetable produce can be grown....
IMO... such systems... focus more on fish farming (aquaculture).... with the plants becoming a secondary stream.... a way of dealing with nutrient waste water...
Most people here look to aquaponics as a "balanced" system of fish and vegetable production ... with minimal cost and maintenance...


Rupert,
it seems that in your mind only the idiot proof version of AP deserves discussion on this forum.
you invariably picture each and every suggestion that deviates from the idiot proof version as inaccessible to everybody except absolute experts

please show some more consideration for people's potential intellect

no aggression intended

frank

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PostPosted: Dec 31st, '08, 19:58 
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Frank, your posts on this forum have improved dramatically, but 3kg per 100l is about the limit for the filtration of the beds. You can pump as much water as you like, but the bed will only absorb so much nutrients.

Been there, tried that.

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PostPosted: Dec 31st, '08, 21:46 
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Outbackozzie wrote:
Frank, your posts on this forum have improved dramatically, but 3kg per 100l is about the limit for the filtration of the beds. You can pump as much water as you like, but the bed will only absorb so much nutrients.
Been there, tried that.

OBO, thanks for noticing and acknowledging

but if it were not for my relentless efforts in showing that my message is what it's all about, not my wrongly perceived attitude or personality,
you and many others would not have noticed my efforts in improving my posts which dates from months ago

If, faced with the fierce opposition, I would have given up, many notions in AP would have remained unchallenged
maybe not all I brought forward, but some of them no doubt deserve questioning
that was, is and will stay my message, no matter the shocking effect and the therefore expectable opposition

I absolutely contest the density limit of 3 kg/100 l where the fish are concerned
many papers agree with me (UVI, one of the pioneers in AP, talks of double density without problem)
all of aquaculture agrees with me (I have visited and seen with my own eyes a catfish farm that successfully breeds 600 kg/m³, 10 tons/yr !!!)

I am opposed to intensive aquaculture in se, as it discharges valuable nutrient rich water to the drain
to them it is waste, to us it is a highly valuable resource.

imagine the number of growbeds that could be fed with this water

but we should not throw away the child with the bath water

the achievements of intensive aquaculture are there, not to be denied

they show fish density to be limited by nothing else but stress
water quality is the most important factor in fish stress
water quality is related to nitrification and aeration and solids removal
nitrification is related to recirculation and biofilter capacity
aeration is related to recirculation
solids removal is related to recirculation
biofilter capacity is related to recirculation

the key word that keeps popping up is recirculation, recirculation, recirculation

there is no reason whatsoever to reject the results or the practices of intensive aquaculture (except for the use of chemicals)

I have studied all of this in depth

I am convinced that one day, somewhere, a person will build an AP system that ecologically and economically combines far higher densities than we now can imagine with far more growbeds than we are seeing as the reasonable ratio now to make sure biofiltration needs are met

or with the insertion of an adequate biofilter, which will ensure water quality for the fish, make nutrients diversion to the plants much more efficient, with much less evaporation, much less temperature changes caused by the growbeds, much lower energy demands for pumping
this system will also allow for a greater variety of plants, from water loving to plants that prefer dryer soil

in other words, systems that will be better for fish health, produce more plants, a bigger choice of plants, cost less in exploitation

such a system does not necessarily suppose Murphy inviting changes. I strongly object to this ever raised objection.

I am not the only one to think so. Many people are slowly accepting these logical reasonings.

the first step to make this possible is to accept that fish density must not be expressed in kg/m³, but in kg/m³/hr,
why? because of the importance of recirculation

want proof ex absurdo (out of the absurd)?
3 kg/m³ fish density is unsustainable if there is no recirculation

the only thing that will change my mind is proof that densities of over 3 kg/m² influence fish stress in a negative way
lots of papers contest that
cannibalism is greatly reduced with increasing fish density
lots of papers confirm this

excuse again the ranting
but, as with the pump efficiency subject, I feel the need of pressing my point

thanks for reading

a happy 2009 to all

frank

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PostPosted: Dec 31st, '08, 21:54 
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cool, good post frank, I shall look forward to trialling :)

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PostPosted: Dec 31st, '08, 23:29 
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Aye, but when some one kinda new to all this asks, what is the quick rule of thumb about how much flood and drain media filled grow bed I need for a given weight of fish, the answer is still gonna be 3 kg of fish per 100 l of grow bed. You might sometimes see a mention of 6kg of fish per 100 l of fish tank per 200 l of grow bed but it still comes down to about 3 kg of fish per 100 l of grow bed.

Yes that is a conservative answer but most of us would rather start newbies off with conservative success rather than high density failure. Once people get the hang of it, they will do what they like but I don't want to mess them up from the beginning.

It is ok to have the high tech discussions about possible ways to create AP systems that can deal with higher densities. Do remember than UVI is using different methods than flood and drain gravel beds. They have other types of bio-filtration so their methods are probably more accurately measured in flow rate. Not necessarily the case with flood and drain gravel beds. Those type of biofilters are serving mulit purpose functions since they are also solids filters and the plant growing space/support.

Please do remember that sometimes when people read the forum, they tend to skim (there is so much info here) so when making a very important point it can be dangerous to make it too in depth and technical where a person might only catch part of it yet try to build a system based on only part of the information.

Saddly many of the terrible fish death stories come from people trying to put up a system with only part of the info they need or being too impatient.

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PostPosted: Jan 1st, '09, 07:19 
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TCLynx wrote:
Aye, but when some one kinda new to all this asks, what is the quick rule of thumb about how much flood and drain media filled grow bed I need for a given weight of fish, the answer is still gonna be 3 kg of fish per 100 l of grow bed. You might sometimes see a mention of 6kg of fish per 100 l of fish tank per 200 l of grow bed but it still comes down to about 3 kg of fish per 100 l of grow bed.

Yes that is a conservative answer but most of us would rather start newbies off with conservative success rather than high density failure. Once people get the hang of it, they will do what they like but I don't want to mess them up from the beginning.

It is ok to have the high tech discussions about possible ways to create AP systems that can deal with higher densities. Do remember than UVI is using different methods than flood and drain gravel beds. They have other types of bio-filtration so their methods are probably more accurately measured in flow rate. Not necessarily the case with flood and drain gravel beds. Those type of biofilters are serving mulit purpose functions since they are also solids filters and the plant growing space/support.

Please do remember that sometimes when people read the forum, they tend to skim (there is so much info here) so when making a very important point it can be dangerous to make it too in depth and technical where a person might only catch part of it yet try to build a system based on only part of the information.

Saddly many of the terrible fish death stories come from people trying to put up a system with only part of the info they need or being too impatient.


I can live with that, TCL,
partially
as it is indeed starting up a system with only part of the info that kills fish
recirculation rate is of the highest importance
as insufficient recirculation = danger for the fish

if a newbie asks the density question it should be answered completely, not partially
half answers are what kills fish
so still the answer is not just 3 kg/m³
but 3 kg/m³ at a recirculation rate of once per hour

my answer would be:
Quote:
at a recirculation rate of once per hour a density of 3 kg/m³ is considered by most of us a safe place to start
with a 1/1 growbed ratio well colonized with bacteria
both lower recirculation rates at this density and higher density at this circulation rate bring your fish in the danger zone
higher recirculation rates, though not necessary, will enhance aeration and water quality


frank

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PostPosted: Jan 1st, '09, 08:14 
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But the number is 3 kg of fish per 100 l of grow bed, not per meter cubed of water.

You could have 3 kg of fish in 50 l of water hooked to 100 l of grow bed with a water flow rate of 50-100 l per hour. Trying to state it that way is kinda a mouthful.

Lets see, how better to state it? I know we like to tell people that they should have a flow rate equal to their tank volume per hour but that is generally aimed at people who are stocking somewhere approaching 3 kg of fish per 100 l of fish tank. If some one were stocking more like 3 kg of fish per 1000 l of fish tank, it might not be necessary to have the flow rate per hour equal the volume of the fish tank.

So does anyone have a recommendation on needed flow rate for something like a swimming pool system with very low stocking density?

What would be a good way for us to state this in an easy to remember and share manner? Seeing as flow rate is important but is saying you need 100 l of grow bed per 3 kg of fish per 50 l per hour really make sense?

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PostPosted: Jan 1st, '09, 08:16 
hygicell wrote:
my answer would be:
Quote:
at a recirculation rate of once per hour a density of 3 kg/m³ is considered by most of us a safe place to start
with a 1/1 growbed ratio well colonized with bacteria
both lower recirculation rates at this density and higher density at this circulation rate bring your fish in the danger zone
higher recirculation rates, though not necessary, will enhance aeration and water quality


frank


Yep.... you could say that Frank..... and some people new to the AP concept may through prior knowledge or intuiative ability understand it and be able to project and relate it to their first system design....

Others might sit there scratching their heads going m3 of what????....

Or ....

You could just say 3kg/100L.... and ensure that the volume of the fish tank is turned over at least once per hour....

Which almost anyone can understand and apply... and which ultimately acheives the same end result...

And this is what has been said constantly and continuously for several years....

Many posts within the forum relate information about flow rates and volume turnover in much greater detail....

What you're saying isn't new or some previously undiscovered startling observation....

It's just expressed as a simple "constant" baseline to enable people to grasp the basic concepts and requirements for a successful system....


And where does the "m3" come from anyway .... a cubic metre of water??? ... isn't that in fact 1000L.... not 100L... ????


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PostPosted: Jan 1st, '09, 08:18 
Ditto TCL.....

And why re-invent the wheel??? .... you can spray paint your own wheel with pretty colours and patterns if you want.... but it's still a round rolling thing.... :lol:


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PostPosted: Jan 1st, '09, 08:45 
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RupertofOZ wrote:
Ditto TCL.....
And why re-invent the wheel??? .... you can spray paint your own wheel with pretty colours and patterns if you want.... but it's still a round rolling thing.... :lol:

I appreciate your experience more than I can express, Rupert.
but you have so far shown no readiness whatsoever to re-invent anything, nor even to much needed rephrasing
wheels now are a long way from when they were invented

excuse me with the m³ confusion, I went into the mist there and humbly admit this
it is because a factor per 100 liters is unusual, factors per m³ are more common

but the mistake is mine

so I will rephrase my answer:
Quote:
at a recirculation rate (of fish tank water) of once per hour, a density of 30 kg (of fish) /m³ (of fish tank volume) (1 m³=1000 l) is considered by most of us a safe place to start
with a 1/1 growbed ratio well colonized with bacteria
both lower recirculation rates at this density and higher density at this circulation rate bring your fish in the danger zone
higher recirculation rates, though not necessary, will enhance aeration and water quality


please comment on what could be confusing in this answer

I exaggerate in the first sentence, I know,
I'm just nagging you a bit :geek:
wine and beer on new year celebration might be responsible

of course my responsibility is not up to questioning :geek: :geek: :geek:

happy 2009

frank

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PostPosted: Jan 1st, '09, 08:50 
Quote:
but you have so far shown no readiness whatsoever to re-invent anything, nor even to much needed rephrasing


Not a question of readiness Frank.... just a question as to whether in fact the need exists to meet our purposes....

You're the only one that seems to think it needs re-phrasing.... as with many things....

Kewl... you want to take ownership of the "wheel" by rephrasing/rebranding/rebagding/re-marketing it.... go for it....

Were/are you a sales or marketing manager??? ... :lol:


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PostPosted: Jan 1st, '09, 08:54 
P.S ...

30kg/1000L (m3) is considered an reasonable and safe stocking density in many RAS systems ...

Yes you can push it past that.... way past it with specific species of fish... and the appropriate auxillary equipment.....

All of which relate to bio-filtration.... and external provision/application of aeration..... :wink:


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PostPosted: Jan 1st, '09, 09:22 
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so recirculation rate has no relevance at all?

I am the silly stupid old Belgian who is the ONLY one who thinks this is of some importance?

I am not claiming ownership of anything, least of all the wheel

just contesting your ownership of all AP systems and the way they should be constructed

I repeat my respect for your experience, Rupert
and appreciate your efforts in trying to avoid us "newbies" to commit mistakes

but you reject all experience of others on all subjects
and the way you react shows that ten years from now you will still keep treating us as silly inexperienced newbies

you know it all, don't you?

I have posted many relevant issues if only the need for questioning
you have contested them all

am I invading your territory or what?

frank

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PostPosted: Jan 1st, '09, 09:35 
Quote:
so recirculation rate has no relevance at all?


NOBODY has EVER suggested that Frank.... and as I said recirculation rates have been discussed many, many times before....

And are constantly referenced (for the suggested stocking densitities) as equivalent to turning over the tank volume at least once per hour.... as is suggested as a minimum for all RAS systems.... (depending on density)....

Read through the forum Frank.... it has been consistently so.......

Quote:
but you reject all experience of others on all subjects
and the way you react shows that ten years from now you will still keep treating us as silly inexperienced newbies

you know it all, don't you?

I have posted many relevant issues if only the need for questioning
you have contested them all

am I invading your territory or what?


Now you're just insulting me personally Frank... and frankly are pissing me off... crawl back in your dark lonely hole troll.....

It's been said before Frank... just cos YOU say so doesn't make it so....

Yep I question, debate and learn..... YOUR ideas (perhaps in some degree) may turn out to have some validity....

But most of them are totally opposed to the way that things are done by most people... in aquaculture, RAS, and AP....

I think it beholds to YOU.... to build, data collect and present... your theories in a real live system... rather than in intellectual postulation.....


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PostPosted: Jan 1st, '09, 09:46 
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I think making post more accessible for newbies is a good idea. Too much heavy stuff and people tend to skim. It takes some time to work out it is easier to skip Franks posts and just read the replys. :mrgreen:

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