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PostPosted: Jan 1st, '09, 10:09 
Frank there are many factors involved with successful RAS operations.... pH, TAN, DO, feed rates, flow rates etc...

Many of the interactions, while reasonably well known.... are complex.... and costly to address.... and some just aren't directly applicable to a backyard AP system....

If you want to run an intensive RAS system... then yes... you will have to understand ... and implement solutions to all the factors...

Follow some basic guidelines... and an AP system is a snap... each to their own....

Here's a few examples... of differing complexity.... but a common bottom line....

Intensive
The most popular growout systems for Murray cod in Victoria are intensive recirculating tank systems (RAS). Murray cod have proven to be very tolerant of high stocking densities (80-150 kg/m³) but oxygen injection is required with very high stocking levels. Murray cod display efficient food conversion (<1.5:1) in these systems with medium-fast growth rates (2g to 500-1000g in 12 months). Survival rates are >80%, but this is dependent on the management of water quality and good fish husbandry techniques. Smaller recirculation systems have stocking rates of 30-40 kg/m³, FCRs of 1.5-2.0 and fish reach market size in around 12-18 months. However, lower stocking densities generally reduce the risk of system failure, as there is a lower load on the biological filter.


The effect of stocking density upon the hydrodynamics of a circular tank, configured in a recirculation system, was investigated. Red drums Sciaenops ocellatus of approximately 140 g wet weight, were stocked at five rates varying from 0 to 12 kg m− 3. The impact of the presence of fish upon tank hydrodynamics was established using in-tank-based Rhodamine WT fluorometry at a flow rate of 0.23 l s− 1 (tank exchange rate of 1.9 h− 1). With increasing numbers of animals, curvilinear relationships were observed for dispersion coefficients and tank mixing times. Stocking densities of 3, 6, 9 and 12 kg m− 3 resulted in a 0.2-, 0.5-, 2.4-, and 3.2-fold decrease in mixing time relative to that observed for empty tanks



In another forum it is wrote:
I operate several freshwater RAS systems in South Australia and have seen many others within the state. These systems run at moderate stocking densities (50-100 kg /cubic meter). All of these systems are very turbid despite continual filtration though 50 micron rotating drum filters and sumps which process the volume of the systems at least once per hour.

I have come to the conclusion that the turbidity is mainly due to a bacterial colonization of the water column. I think this because the turbidity acts in the same manner as high density aglae cultures ie. turbidity increases rapidly and lingers, followed by sudden death and rapid clarification of the system. This seems to happen independently to levels of nitrogeonous wastes.

I have tried to combat this problem using small doses of formalin and chloramine-t which work with varying success. These chemicals also adversly affect biological filtration, thus i would like to find a better way to combat this problem. i have also tried many probiotics / beneficial bacteria, none of which work.

If anyone knows what im talking about and hase a good solution i would love to hear it.
.....

Yes, i agree ozone does indeed help the problem, especially when used in conjunction with with protein skimmers.

We have attempted this on a small scale, however we found that we needed a large, expensive ozone generator and we had to inject pure oxygen into the machine to icrease it's ozone gerneration capacity, furthermore the cost of the stainless steel reaction chambers was high as large units were necessary to achieve the contact period necessary to 'nuke' the bugs. Also the necessity for protein skimmers, ozone destructor units and ORP meters to regulate its operation made it very costly and even then we were not entirely happy with its performance. I dread to think what the cost may be to set up a system to treat a large system with high stocking densities.

We have also tried passing the system through a 10 micron filter once per hour with no real improvement.


The concentration of DO present in water is affected by various factors, including altitude above sea level, water temperature and consumption rate, an increase in any of these factors reduces the amount of oxygen present in the water. A system that is designed to support a certain density of fish at sea level may not function as well if the water temperature, altitude or stocking density is increased. Furthermore, different species have different sensitivities to the DO concentration for example salmonids typically require minimum DO levels of around 6.0mg/L and tilapia require a minimum of 5mg/L. Now, the oxygen holding capacity of water at 16C (trout) is much higher than the oxygen holding capacity of water at 28C (tilapia), assuming the same altitude. Furthermore, tilapia are commonly stocked at higher densities than trout, increasing the demand for oxygen in a tilapia production facility. As roughly 250g of oxygen is consumed for every kilogram of feed eaten by the fish, the system design needs to take all these factors into consideration to ensure sufficient oxygen is available for the optimal growth and health of the fish being cultured.

At low to medium stocking densities water exchange or aeration are adequate for maintaining acceptable DO levels, and these methods are typically employed in raceways, and cages and earth ponds. Within a RAS the temperature of the water is controlled (usually heated) to optimal levels to promote rapid growth of the stock. Large water changes, such as are required to maintain DO levels, are not practical as this means the replacement water must be heated (or cooled) to the appropriate temperature, and this is an expensive process. Aeration is therefore used to maintain oxygen levels within RASs stocked at low to medium levels (<25 - 50kg/m3 - species dependant). Once densities of fish exceed the level where aeration is adequate to maintain DO levels, gaseous or liquid oxygen is added to the system to maintain appropriate DO levels within the water.


One of the key problems in RAS relates to the load of suspended solids and in particular to
very fine particles. The presence and accumulation of particulate wastes in RAS (faeces,
uneaten feed, and bacteria flocs) will impact negatively the water quality by affecting the
performance efficiency of the water treatment units. High suspended solids load has many
disadvantages:
o Particulate matter consumes oxygen during biological degradation which will
decrease the availability of oxygen for fish in culture (Rosenthal, 1997; Davidson
and Summerfelt, 2005).
o The brake down of organic wastes will increase the TAN concentration in the water
affecting nitrification (Liao and Mayo, 1974; Spotte, 1979; Davidson and
Summerfelt, 2005; Chen et al., 2006). Small quantities of unionized ammonia can
be toxic for epithelial tissues and disturb the elimination of protein metabolites
across gills (Peters et al., 1984).
o Solids support the growth of heterotrophic bacteria which can outgrow and compete
with nitrifyers. The nitrification process is strongly inhibited by heterotrophic
processes when high amounts of organic carbon are present (Zhu and Chen, 2001).
o Suspended solids offer an ideal temporary substrate for facultative pathogens while
they try to find a final host. Bullock et al. (1994) inferred that suspended solids may
be involved in bacteria gill disease (BGD) outbreak. Noble and Summerfelt (1996)
described that beside opportunistic microorganisms, non-infectious problems
prevail as high levels of suspended solids have caused mortalities in RAS.
o Particles can potentially clog biofilters and reduce their efficiency (Chen et al.,
1993; Rosenthal, 1997).
o Excessive solid loads can cause plugging within aeration columns, screens, and
spray nozzles orifices, which could ultimately result in system failure (Davidson
and Summerfelt, 2005).
o The organic C/N ratios in the water will negatively affect the efficiency of nitrifyers
(Rosenthal, 1997; Ebeling et al., 2006).
o The accumulation of solids can create anoxic conditions favourable for bacteria
responsible for the production of geosmin and 2-methylisoborneol causing offflavours
in cultured fish (Tucker and Martin, 1991).
o Gill tissue can be damaged by particles (Rosenthal, 1997) during feeding, drinking,
and breathing. Bullock et al. (1994) suspected that small suspended solids could
irritate gill tissue and provide an injured surface for attachment of any bacteria
(BGD) present in the water. Peters et al. (1984) found out that fin and gill lesions in
rainbow trout were induced partly by the accumulation of excretory and
decomposition products. Madetoja et al. (2000) showed that skin and mucus
abrasion dramatically enhanced the invasion of pathogenic agents into the fish.
o Fish vision can be affected by high suspended solids load, disturbing the recognition
of feed.
The proper management of suspended solids is one of the key factors determining the
successful operation of recirculating systems because of the elucidated potential impacts.
The design of a RAS to achieve the desired solid elimination has to take the following
aspects into consideration:
o The more quickly solids are removed from the water the less time they have to
break down and consequently less oxygen will be consumed by attached bacteria
(Bullock et al., 1994, 1997; Rosenthal, 1997; Davidson and Summerfelt, 2005).
Long residence times for particles in the system will affect their size due to share
forces and microbial degradation. Substances are leaching faster from smaller
particles than from big ones. Small particles, however, are more difficult to remove
from the culture water because of size and the proximity to water density.
o The methods to remove solids (sedimentation, filtration, and/or flotation) have to be
able to eliminate particles over a wide range of sizes. Normally a combination of
removal techniques are needed (Waller et al., 2003a; Orellana et al., 2005) specially
for the elimination of fine solids fraction (<20 μm) that do not settle in conventional
treatment processes such as gravity settling and microscreen, and accumulate in the
culture medium over time (Chen et al., 1993; Chen et al., 1994; Langer et al., 1996;
Rosenthal, 1997; Waller, 2001; Viadero and Noblet, 2002; Orellana et al., 2005).
o The size of fish and the water flow rates seem to be two closely related factors that
determine the characteristic of solid waste and because fish size and feed size are
known, these characteristics can largely be predicted. Small fish produce small
particles and need high quantities of feed per unit weight in order to satisfy their
energy requirements, while big fish produce larger particles and need less feed per
unit of biomass, compensated for by a relatively lower growth rate (Franco-Nava et
al., 2004). The amount, characteristics, and size of solids indirectly determine the
choice of methods for efficient removal.
o High stocking densities are often aimed for (depending on the species) to boost the
profitability of a RAS. High stocking densities allow more fish biomass to be
produced per unit of culture. However, increasing stocking densities require a better
management of solid removal and highly reliable removal techniques. Solid loads
will increase rapidly. Waste removal from the system has to be efficient and
becomes costly if mechanical means are no longer sufficient.


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PostPosted: Jan 1st, '09, 10:47 
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you, Rupert, and you, Dufflight, win
I give up (and this time I mean it) discussing this and other subjects with you

you are both systematically trying to shut me up
not only here,
the "Hygicell's pump efficiency discussion" clearly shows how you do it:

by posting a myriad of reactions that have nothing whatsoever to do with the subject of pump efficiency
smothering the subject with lengthy posts
like your last one on this thread, Rupert
which, by the way contains information that contradicts your assumptions:
Quote:
These systems run at moderate stocking densities (50-100 kg /cubic meter).

questioning the data and links you yourselves provide
never accepting the results when they are put to the test
always insinuating that I have no experience whatsoever
insinuating that I manipulate numbers
insinuating that I have no system
not ever acknowledging frankly that I may (may !!!) have a point
stating for truth that I am the ONLY one with unanswered questions
finally questioning my attitude
treating me as the enemy
a tactic you have used before on more than one occasion
viewtopic.php?f=8&t=4661&st=0&sk=t&sd=a&start=165

I have no more time for this
pure waste of energy

frank

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PostPosted: Jan 1st, '09, 10:54 
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Geez Guy's I didnt'y want to start WW3 :cry:
I appreciate all of the assistance from everyone, I do get what you are setting out Frank?
Here is what I have gleaned so far,
Yep I have a 30KL pool,
I dont have 30Kl/30m3 of grow bed
I do have 10KL/10m3 of grow bed, not counting my BYAP 3 bed kit system which I am discounting as it is already set up.
I dont want to have a RAS industrial style system
But it will be integrated into the BYAP kit system by dropping the supplied Ebara pump into the pool (I will work out the flow and head) and using that to pump to all of the IBC's and existing beds, using the existing kit tank as a sump tank with a gravity overflow back into the pool.
Running the pump at least once per hour, I have been doing this already with increased run times during the hottest part of the day to keep the system cooler (a portion of the grow beds are in full sun, in inland WA that means HOT), keeping a good eye on the system as it establishes/integrates with the existing
I want to increase my intensity with cold weather trout, stocking in the pool only, leaving the BYAP kit as a garden pond with goldies, Koi,yabbies and the last remaining Silver Perch that hopefully will be going in at the end of this month to start the edible fish off with a breed that co exists with the pretty fish
From my understanding, I should be safe with 30kg of grown fish to every 1m3 of grow bed, therefore 300kg of grown fish (supposing 1kg per) is safe :?:
That is a heck of a lot of fish to smoke, freeze, pattie etc so I reckon that I wont be going to that sort of density. (mind you it is less than a fish a day annually, mmm? :roll:)
Righto you blokes, put the boxing gloves away and tell me if I have got any of the above wrong please
Remember that it is Happy New Year :flower: not carry on like the Palestinians and Israelis :twisted:
Iv'e got the smilies down pat , now to suss the photo's out

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PostPosted: Jan 1st, '09, 10:59 
Bullocks.... this thread is about ratios.....

In the other thread ... you introduced the postulation that pumped water flow alone was sufficient for aeration....

I have been pointing out that what you suggest is contrary to most accepted methodology....

And appears to be untested... even by yourself....

It is you Frank that is always challenging others (not necessarily a bad thing) ... and react when others query your premises....

Build your system Frank.... post it... with pictures, as this helps people conceptualise how it works....

And stock it to what you feel is an acheivable density, employing your preferred methods of aeration.....

We'll eagerly await the results.... and if there is validity in some of your design proposals... then I'm sure that some people will incorporate them.... such is knowledge advanced...

I merely highlight, and will continue to do so.... for the benefit of those new to the forum and AP.... that here are some basics upon which to build and develope your understanding of aquaponics....

I make no apology for that.....


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PostPosted: Jan 1st, '09, 12:12 
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RupertofOZ wrote:
In the other thread ... you introduced the postulation that pumped water flow alone was sufficient for aeration....

I have been pointing out that what you suggest is contrary to most accepted methodology....


Hay Rupe, I haven't read this "other thread" but when you mention pumped water flow alone possibly not being enough aeration (at least that is what the quote of a mention seems to be saying) I wonder if that just means pumping water around with no splashing? My big system only gets air bubblers when the power goes out. Otherwise all aeration is through the movement and pumping of water. Granted, my pump normally runs 24/7 and my system has something of a waterfall designed into it.

Ah, but since I've avoided reading the other thread I must be taking that comment totally out of context.

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PostPosted: Jan 1st, '09, 12:28 
Yep TCL... pumping water and acheiving aeration through waterfalls/cascades/baffles/trickle towers/ flood & drain growbeds.... all taken as accepted, by myself anyway...

The arguement seems to be that aeration by "airstones", blowers etc ... are totally inefficient (probably true to a large degree)... and have no place in an AP system...

And that low watt pumps recirculating water to the fish tank (via what I'm not sure).... or just "welling" the water within the tank is sufficient for aeration...

However, even the low watt pumps seem to be inherently inefficient, so we're back where we started...

And I would be concerned as to possible pump failure and aeration if no supplemntary aeration was available.... as I can attest only too well .... :roll:


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PostPosted: Jan 1st, '09, 12:34 
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Jim, you assumptions are correct :)

How are the yabbies going? You do have your own thread as well :mrgreen:

viewtopic.php?f=18&t=4543

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PostPosted: Jan 1st, '09, 13:03 
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Man this is outta control so as a newbie I will put in my 20c worth (about 13c US)
Everything has to be tried, but no point throwing figures around without backing it up, who knows things may work differently in Belgium as the climate is totally different, for me I have tried a few experiments, most failed but finally I think I am onto something as I have successfully turned the Missus's little system from a green can't see Jack to a crystal clear functioning system. I have been out into forests down south WA that have natural water soaks, some quite large but not much running water, I have taken note of what lives in them as they are crystal clear, I have put a few of the things living in soaks into my little system like Minnows, Pygmy Perch and these little oval shaped bugs with big back legs for swimming (we call them Boatmen) and the imported from NSW freshwater mussels (12 in 200lt) this with a pump and a 50lt GB of Blue Metal and clay balls cleaned up the tank, now then added 6 huge gold fish and something easy to grow Apple Mint after 4 weeks no change in tank, and mint is growing to well plus everything is living happily together, this 200lt experiment is going to turn into a 2 x 3000lt tank experiment, will have my eco system with Marron in one tank and Redfin or Silvers in the other, tanks will be connected by a 75mm fitting at the bottom of tanks, will put some 19mm square mesh over opening, plus 1000lt of GB's and 10,000 LPH pump, will pump out of the Redfin tank and drain back into the Eco tank with the idea that what the GB's miss the eco tank will sort out, but how many fish? I know what the eco tank will take with Marron, Mussels, Pygmy Perch etc but my fish tank? 3kg per 100lt GB = 30 fish I may go for 50 to start and see what happens, will it work? N.F.I but these things have to be tried, the Eco tank contains things that are edible but take around 3 years to grow whilst the fish tank has quick growers that crap a lot so will the 2 systems even out?
But I suppose that the end scenario is that no one person probably is right, Rupe, conventional is obviously the best a efficient way to go but then why not experiment, if we didn't experiment the the Wheel would still be a Wheel made from round rock and driving nothing really, but Frank, rupe is correct to say it is all right having theories but no point arguing about them if you can't back them up, I can back up all my failures, my success I will photograph when the temp drops below 40c deg and post in My Missus's little system thread, and the next experiment about a month away, so chill out 8)

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PostPosted: Jan 9th, '10, 21:26 
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If I'm doing continuous flow, do I need a sump tank?


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PostPosted: Jan 10th, '10, 18:22 
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whoa!!
I'll stick to the 'KISS' principle
3 KG of fish to 100 GB.
just want yummy veggies and fish??

regards

matt.

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PostPosted: Jan 11th, '10, 00:04 
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If running a continuous system without any flood and drain elements, a sump is not needed.

In fact, Sump tanks are only needed if you want to control or eliminate water fluctuations in the fish tank or if you wish to have more grow bed volume than you have fish tank volume.

If you are doing continually flooded grow beds, then no you don't need a sump tank. You may need additional aeration though and extra care to avoid issues with root rot might be necessary (as in cleaning all potting medium off of roots before planting seedlings into the grow beds.)

Also now that the indexing valves are available, one could do a system with flood and drain beds and more grow beds than fish tank and still avoid the need for a sump tank.

However, I am running an indexing valve and perhaps I don't really need a sump tank but I prefer the CHIFT PIST method and like having my pump work from a clean water sump. Additionally, the huge amount of extra water my system can contain certainly helps stabilize the system water temperatures and water quality.

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PostPosted: Jan 11th, '10, 02:03 
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peter k wrote:
If I'm doing continuous flow, do I need a sump tank?


As TCLynx pointed out, a sump is not needed (but may be nice) if you have nothing that floods and drains. Do you have any or is your system continuous flow? If you do have some, how much compared to the volume of your fish tank?

My biggest system has no sump and the water level fluctuates by about 4" (10cm), so it does not bother the fish. On the other hand, I really can not have many fish as I am limited by the growbed. On the third hand, if my power goes out for a day the fish will still be ok although the plants will suffer.

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PostPosted: Jan 25th, '10, 16:02 
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I think I'm ready to start a system!! I'll put forward the design ratios for comment and input of your wisdom.

My fish tank will be 3000 x 800 x 750mm deep (Gross volume 1800 litres). Allowing 50mm freeboard, the useable volume is 1680 litres. Surface area 2.4 square metres.

Three grow beds (GB) each 3000 x 580 x 350mm deep (610 litres each). Allowing 20mm freeboard effective fill depth becomes 330mm and volume becomes 560 litres.

Three at 560 = 1680 litres. Note gross volume of growth beds equals volume of fish tank.

Surface area of garden beds = 3 x 1.74 = 5.22 square metres.

Allowing that grow beds contain 60% media (stones), then the water capacity of each bed = 224 litres.

My idea is to get a pump with about 700 litres per hour capacity. Run it for 20 minutes to each bed. Over the space of one hour, each bed gets its fill of 224 litres. Each bed is drained back through a valve throttled to take about 30 or 40 minutes.

The system gets filled with 1680 litres in the fish tank plus 224 litres up in one growth bed = total 1904 litres.

As long as the pump keeps running, the water level in the fish tank remains steady.

If the pump fails, then I have an overflow from the fish tank into a reserve tank of >224 litres capacity.

When the pump re-starts, I have to pump the water from the reserve tank back into the system.

Can anybody help with this : Some method to divert the pumped water for 20 minutes to each growth bed in turn, perhaps a solenoid operated rotary/distributor valve?


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PostPosted: Jan 25th, '10, 16:33 
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Hi Ken

Observations from your post:

Total volume of system is 1904 litres but only pumping 700 litres per hour. May not be enough water movement. Better if you can turn over the entire volume of the tank each hour or close too.

To be honest I wouldn't worry about the extra 224 litres in the grow bed with the associated little sump and pump. If you are going to the trouble of digging a hole for a sump then I'd make it a big hole/sump and build the system CHIFT PIST.

If not CHIFT PIST then I still wouldn't worry about the little sump. I reckon get a bigger pump and one of Rupert's Spiders Valves and just pump more water more often.

Hope that helps :)

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PostPosted: Jan 26th, '10, 00:14 
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+1

Remember that a pump rated for 700 liters will almost never give you that. I'd say go double and be sure.

What is your plan on getting water from the overflow back into the system after a failure?

kenb wrote:
As long as the pump keeps running, the water level in the fish tank remains steady.

Well, not exactly steady, but close enough for the fish: it will depend on the speed at which water flows from your growbeds back into your system.

Have fun!

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