Jeffers jumps in

[jeffers]

Hi! I'm living in the lower mid north of South Australia on what used to be a wheatfield. My wife & I built a house and a vegie garden and planted about 800 trees, all in the space of 2 years. We built a pergola out the back (about 10 metres by 4 metres) and thought we might use this area for aquaponics after some contact with Joel in WA. The area falls a bit short of the ideal layed out in his book, but I think we can still do something substantial. I was delighted to find a forum to discuss the possibilities of this project.
Murray, I'm really interested in your growbeds - in order to get the ratio of fishtank to grow bed volume in the ballpark, I really need rectangular beds as follows:
2 X 2 metre square beds
1 X 1.5 metre X 1 metre bed
1 X 2 metre X 1 metre bed
1 X 1 metre X 0.6 metre bed
three smaller growbeds around the top of the main fishtank each about 0.8metres in diameter, probably made from galvanised iron
Murray,are you able to build grow tanks to order, and if so, do you have any feel for the cost os shipping for these?
I want the fishtank to be 2 metres in diameter and 0.9 metres deep, and will probably have this made out of galvanised iron.
The growbeds will be very heavy, and I'm planning to support them on concrete filled bessa blocks overlayed with joists and bearers.
Am I mad or could this work?
I've spent a lot of time designing this on google sketchup and the plans look good, it's the practicalities I'm going to need help with
Thanks
Jeffers

[Murray]

Hi Jeffers,
The area you have will allow you to have a good sized system.
Re the grow beds. We have two sizes the 585 ltr one and the 230 ltr size. While it is possible to make custom sizes of grow bed, it would prove to be very expensive and therefore not practical. It would be best to rethink your layout a bit to use equipment that is available.
The standard grow beds can be seen here http://www.aquaponics.net.au/category1_1.htm
Your idea re the grow bed stands is right on the money....see the article in our latest Practical Aquaponics Mag which is avbl for download now on this Forum. Grow Bed stands made from concrete block and sleepers are really excellent.
If you need some pricing, please PM me for special "Members of this Forum"
prices
Murray

[RupertofOZ]

Hi Jeffers,

Would be good to see your sketchup diagrams in order to help with specific questions that you may have. Could you post them.

Edited :

Just looking myself... not sure how or if you can actually do that as yet... I'll PM the mods.

[jeffers]

Thanks Rupert - as you can see from Murray's comments I may have to do some re designing, But would be happy for you to have a look when that's done. Murray, thanks for your info - I downloaded the e mag and see what you're getting at. I was actually going to do something like a floor support, but your idea looks simpler. Can you give me any idea of the cost of transport for two large beds and two small ones to Adelaide SA? I could come down and get them from there. Could you give me some advice about the fish stocking capacity of such a system? Even if I have to reduce the size of the growbed area initially, I'm thinking I'll keep the same size tank with fewer fish to allow for future expansion
Thanks for your quick reply guys
jeffers

[Murray]

Hi Jeffers, Re stocking levels.
As a rule of thumb, the max stocking levels in Aquaponics systems is to assume 1kg of grown out fish per 10 ltrs of fish tank water. So if you have a 3000 ltr tank you could start with 300 fingerlings. I am assuming Silver Perch.

It is common in the aquaculture industry to stock at very much higher levels than this, so don't think the fish will be overcrowded or being treated badly. Fish tend to school up anyway. In a home situation this level of stocking is very manageable. If you keep your water quality in good shape and do not over feed everything will be fine.
If you take good care of the fish the rest of your system (veggies) will just follow along.

The good thing for the home aquaponics system is that Silver Perch grow at different rates, and out of that initial batch of fingerlings only a few will reach plate size together. So their growth is staggered allowing for a steady stream of maturing fish.

I will send you a PM re grow bed prices etc.

Murray

[damien little]

is there a specific or recommended amount of plants to service that kind of stocking density? I have heard figures bandied about at half of that being pushing the boundaries.

[RupertofOZ]

Damien, the stocking figures Murray quoted are probably a bit too high to be safely managable for the average person to stock that high requires more of a balancing act and less margin for error.

If all 300 fingerlings grow out to plate sized fish (500gms) then thats 150kg of fish in 3000ltrs => 5kg/100ltrs

(you probably wouldn't get all 300 fish growing out to 500gms at the same time... but lets assume for simplicity)

The safe rule I have seen referenced is about 3kg per 100ltrs, with perhaps a maximum of 6kg per 100ltrs if the systems has the growbed/plant capacity to support that density

Even mainstream aquaculture ventures are beginning to push the envelope at densities > 5-6kg/100ltr and would probably be factoring in a 20% loss rate

In defence of Murrays figures quoted I would point out (sure Murray will correct me if wrong) that higher stocking densities can be acheived by running seperate/additional bio-filters, solids skimmers and/or performing regular water changes

Typically, most backyard systems only utilise the growbeds as biofilters and I think you could only safely get about half that density in the average backyard system. One of the reasons for this is that bio-filters are often expensive... > $300

There's a suggested optimum balance between fish tank size and growbed size of 1:2 ... ie 3000ltr tank would require (and support) 6000ltr of growbed capacity.... how many plants is probably more determined by just how many you can physically fit within the growbed areas and still allow for proper plant growth.....

Ultimately it's all about acheiving a balance between the production of fish nutrient rich water and nitrate uptake by the plants....

You can adjust the first by both stocking density and feed rates.... and even water changes if forced to....nitrate removal can be adjusted by number of plants, capcity of growbeds and type of plants.... some plants - tomatoes for instance (or most fruiting/seeding) plants have a much higher nitrate/nutrient uptake than say a lettuce.....

Ultimately the bacteria in the growbeds multiplies to absorb the amount of nutrients available.....

more growbed capacity => allows more fish or more feed
more fish/more feed => more nitrates available for uptake => more plants
more plants => more nitrate uptake => more feed
less plants (harvesting/transplanting) <= less feed or less fish
less fish <= less growbed capacity required or <= less plants or <= slower plant growth

Its all just like nature... a finely tuned balance

[Murray]

Thanks for that Rupert,
I actually keep much higher densities of fish than 1 fish per 10 ltrs of water. So it is very possible to achieve those levels. But as you alluded to, it requires some close management of the system.
In recent times I have had up to 400 fish in 2300 ltrs of water with more than 40 of them above 1kg in weight. (a lot of those fish now reside in my freezer)
Currently I have 10 around the 1 kg mark with 300 or so smaller ones.
Based on my personal experience I believe that 1 fish per 10 ltrs of water is easily manageable. (that assumes that the fish will grow to approx 1 kg each)
Muzza

[RupertofOZ]

Murray, I’ve always been amazed at the stocking rates you seem to be able to carry….

The only other people I know of that consistently carrying those sorts of rates are the large commercial operations like Taylor Made. And they do so utilizing $150,000 drum filters and $40,000 solids skimmers…. And by running to waste and replacing at least 10-15% of their water volume each day.

Without implying any criticism, as you indicated yourself, these sorts of levels require “close management of the system” and I don’t believe stocking densities this high are sustainable by most in-experienced people starting new systems.

If you break down your current figures, it would appear that (having removed about 10fish/10kg to the fridge :) ) you are currently running ….


10 around the 1 kg mark with 300 or so smaller ones

Assuming the 300 fish range in size from say fingerlings through to plate size (500gm), then you could average the 300 fish out to about 300gms each, totalling about 90kg, plus the 10 fish at a kg each, gives a grand total of about 100kg in the 2,300ltr tank

A ratio of about….4.37kg to 100ltr …. In line with what I referenced as the suggested maximum levels of 5-6kg/100ltr

To achieve these rates takes a level of experience that you have gained over the last 12-18 months and specific management techniques.

I think that it would be of immense benefit to all newcomers if you could give a complete outline of your system and the techniques you use to achieve this level of stocking….

i.e tank size, number of growbeds, use of bio-filters, aeration and percentage volume of water of replacement per week, feed rates etc.

Perhaps a response linked back to your thread might be more appropriate….

http://www.aquaponicshq.com/forums/showthread.php?p=107#post107

[joel]

I'd be very interested to hear how you can recommend stocking fish at a level of 10kg per 100L Murray. I've seen many aquaponic systems over the years, along with many aquaculture systems. I have never seen or heard of an aquaponic system being stocked at such levels.

The suggestion of stocking a system at 10kg per 100L would mean that your system with it's 2300L fish tank could have 230kg of fish in it. Have you had this volume of fish in your system?

[jeffers]

It's great to hear this level of debate about the stocking levels, it's exactly this kind of conversation i had hoped to have with people who are already doing it - I think I'll let the dust settle before making any final decisions.
I'm hoping to start building the system in about a month.
The information on beekeeping in the emag was great - if I get my own hive, does that discourage bees from other hives from visiting the garden? We are lucky enough to have a hive in a large gum tree about 100metres from the house, but honey is out of the question without a 20 metre extension ladder and a lot of health insurance. At the same time I wouldn't want that hive to die out as a result of competition.

[Jimmie]

Interesting stuff re stocking levels. I have been wondering about this myself. About to start putting things together and need to know as much info as I can get on this subject.
Jimmie

[GaryD]

Hi Joel

Welcome to the Aquaponics HQ Forum.

With respect to your post, I suggest you note the following:

Murray did not recommend stocking fish at the rate of 10kg per 100 litres of water. What he, in fact, said was that this figure was a maximum.
Within the same post, he went on to clarify his statement by speaking about the fact that “Silver Perch grow at different rates” – that fish would be harvested as they attained plate size.
The clear inference in this is that, for example, a 3000 litre tank could produce 300kg of fish over a season…..which is exactly how most people would want it. I guess you assumed that he meant that it would all happen at once.
He did not state that he had 230kg of fish in his tank…..and nor to the best of my recollection has he ever made that claim. I guess you assumed that, too.
In fact, in his post, Murray did say that he had “more than one fish per 10 litres of water.” I know this to be true…..he actually had over 400 in the tank at one stage…….but they were all different sizes; exactly as Murray admitted when he said “Currently, I have 10 around the 1kg mark with 300 or so smaller ones.”Let’s assume that Murray did mean 10kg of fish per 100 litres. Where could he have got that idea?

On Saturday 8th July 2006, you made a post to your own forum which reads…

“I found this article by Wilson Lennard (Australia's first PhD in Aquaponics) that I hadn't found before, it's well worth a read and I felt deserved it's own thread. He talks about some amazingly heavy stocking densities in aquaponics systems...."

To quote the article to which you refer in your post of that date…..“If, for example, we take a 1000 L tank containing 100 Kg of fish and feed the tank 2% of the fish body weight per day, we feed 2 Kg of feed per day.”

This seems to conflict with your assertion that you "have never heard of an aquaponic system being stocked at such levels."

For the record, I believe that 100kg per 1000 litres is possible, too. Would I recommend that someone attempt that stocking rate during their learning phase.

Definitely not........and nor did Murray!

I hope that clarifies the situation for you.

Thank you for your contribution.

GaryD

[Macca]

I've gotto admit this whole conversation has confused me a lot. I thought that 10kg per 100 litres was what was being suggested. Although I had noticed a lot of swapping from references to fish # to kg, a number of things led me to believe this including the words:

'As a rule of thumb, the max stocking levels in Aquaponics systems is to assume 1kg of grown out fish per 10 ltrs of fish tank water.'

I guess I just misunderstood. I'm glad you have clarified it Gary because I was now doing my calculations based on a thought I could grow 100 1KG fish in a 1000 litre system - which is the size I am aiming for :confused:

[Murray]

Macca,
If you start with 100 Silver Perch in a 1000 ltr tank they will not all get to 1 kg at the same time.
Let's assume that at the imaginary 1 year mark we take a stock of our Silver Perch.
We will find that we will possibly have 10 or 20 that have reached the magic assumed weight of 1kg, and you will also have the remaining 80 or so at various sizes, some at 900 g, 800 g, 600 g and so on right down to one or two that may not have grown much at all.
That is one of the many wonderful things about Jade and Silver Perch for the home grower. Because fish (a bit like humans) do not all grow at exactly the same rate.
In actual practice you would have started to harvest some of the big ones, possibly as soon as they were around the 800 to 900 g mark (some at about the 8th or 9th month)
In actual practice you will never have 100 x 1 kg fish in your 1000 ltr tank.

The rule of thumb of 1 kg of grown out fish per 10 ltrs of water serves as a method of working out how many fish to start with, and serves as a method of working out how many more fingerlings to get at the 6 or 9 month mark to ensure a steady supply of fish at around the 1 kg mark.
I am sorry I did not explain it better earlier, but I thought I had.

It is just so satisfying to look in my 2300 ltr tank and see those big Silvers cruising around and the little fellers scurrying to get out of their way.
If I could find a way to keep double the amount of fish I would.
I have this terrible compulsion to ring the hatchery and order more fish !!!!!
Murray

[Macca]

Silver perch certainly sound like a great fish - able to grow from fingerling to 1kg in 12 months is fantastic :)

[Murray]

Actually, The Silvers would have to be in very ideal conditions to reach 1kg in a year, more likely to be at 800 or 900 g
Murray

[Macca]

I'd still be happy with that. What would be ideal conditions?

[GaryD]

Hi Macca,

For what it's worth, 1kg of fish per 10 litres/10kg of fish per 100 litres/100kg of fish per 1000 litres is all essentially the same thing.

Where the issue of interpretation comes into it is that you could have 100 kgs of fish in a 1000 litre tanks at any given time.....or you could produce 100kg of fish in a 1000 litre tank over the life of a season (as Murray suggested). Can you see the difference?

Personally, I wouldn't recommend 100kg of fish per 1000 litres if you are new to Aquaponics. There's too little margin for error if things go wrong.

I'd suggest that you start of with a prospective yield of 30-40kg per 1000 litres until you develop the necessary knowledge and skills and (hopefully) you've invested some resources in some backup systems.

I'm about to make a post in my own thread which makes it clear that, regardless of how much experience you might have, you are never immune from a belly flop.

GaryD

[Macca]

I do realise that 100kg per 1000litres = 10kg per 100litres = 1kg per 10litres. That was not what I was querying. You kill some fish Gary LOL (shouldn't laugh - I've killed heaps of ornamentals in my time). Will wait and see what you say in your own area.

[Murray]

Macca,
The right conditions would include such things as ideal temps, good food, (not to be overfed) and excellent water quality in regard to ammonia levels etc. Also, the fish must not not get spooked , when they are stressed they go off their food. I have 3 grand sons that are hard to keep away from the fish tank when they visit. I have copped them trying to poke the big fish with a stick. Sounds aweful, but it makes perfect sense to an 8 year old I'm sure.
Not good for the Silvers....

Murray

[Macca]

Would make sense if it had a sharp end and you were looking for some dinner LOL

[becky]

see, now i'm thorougly confused! not that i'll be putting any kilos in my 2 foot tank.

Is there a standard on kg/fish at any one time OR Kg of fish a system can produce over a season?

Its all too confusing.

Becky

[Macca]

Don't undersell yourself Beck. A stadard 2 foot tank is about 50 litres. Should be able to have 5 big silvers in there.

[GaryD]

Hi Beck,

You could probably accommodate a good handful of fingerlings of most varieties of freshwater fish in your 2 foot aquarium.....up to perhaps 100mm or so.

You can also put a breeding pair of yabbies in a tank of this size - until the babies hatch.

It's a bit small overall to think in terms of growing anything (other than goldfish) to full size.

Many people use such aquaria to prove the concept of aquaponics.

From a personal perspective, if I can't eat it I dont grow it.....so that rules goldfish and similar aquarium fish out for me.

GaryD