Backyard Aquaponics
A place to discuss aquaponics

Stuart - Janet is talking about continuous flow (CF) while you are talking about continuous flood. I ran a small grow-bed like this for some time due to roots clogging soem of the drain - reducing the draining flow.

While it worked okay - I think there could be a few issues depending upon how it was set up, including - anaerobic areas forming in the menium, more DO issues than a F&D system, a need for higher flow rate due to the first 2 issues. The only advantage I can see of continuous flooding over F&D is that the fish tank (or in my case sump) is not depleted of water as the bed is flooded all the time. For me the disadvantages far outweighed the advantages and I was in a position to build a system that would cater for F&D - so I went that way. I would nto rule out having a continuous flood bed as part of my system in the future and I will certainly be running soem DWC at some point.

Aaron - I have about 15 each of silver and jade perch. Will get another 200 when I get the time to pull my finger out.

Steve & VB,

What kind of growth rates are you getting from your fish? Do you know the feed conversion rates your fish are getting? If not, roughly what size are you starting with and getting to over what timeframe?

Aaron.

Those kind of studies will happen when I get my final system in place Aaron. With my current fish there have been significant periods where they have been fed little due to the system not having enough grow-bed space etc. While this is no longer the case - and I am feeding them pretty well (although only once a day), any calcs would be severely affected by the early days.

Having said all this - I have had my fish for about 7 months and I have seen very impressive growth despite the above. I am very confident that in my proper system I will be able to grow out the perch - from fingerling to about 500gms - in 9 months. I think conversion rate for perch may be about 1.5 or 1.7 times food to growth?? A google will find it.

One obstacle to calculating all this sort of stuff also is the fact that one tries to limit as much as possible the handling of the fish. To catch all fish to determing weight periodically is not something I would like to do. Of course can do an averaging thing - but this may not be too acurate as our fish tend to vary a bit in size after a while eventhough they start very similar.

When doing a study on conversion rate in AP - which I will do in some way shape or form eventually - one would of course need to account for all food given - which is normally a lot more than just the pellet food. Mine get various green leaves and different grubs, bugs, worms etc.

Same here, i'm fairly sure it ranges from about 1.4:1 to about 1.7:1 depending on age. Settle on 1.5:1

I've "played" heaps with my system, and as with VB there have been extensive periods of light feeding. Its all done for the greater AP good

My system is operating pretty much where i want it now, so growth rates should be good.

It should be noted that SP will eat the most at around 21C and not feed at all below about 13C (double check these figures)

My catfish are always hungry, and are growing quite well.

EB will be able to give you some definative answers to growth rates as he has the longest standing system, i'm fairly sure he gets them to plate size
(500gm?) in 6 months or so. EB?

Hey Aaron,

I grew a crop of Barra from 45g fingerlings to 445g fish in 6 months. I could possibly have pushed them a little harder as well, generally they were only fed once a day. Of course thats Barra, the perch are a bit slower..

Here is a couple of extracts on SP and JP FCR's, remember these are figures from hatcheries/ponds

Silver Perch
Food conversion ratios (FCR's) for silver perch are generally in the range of 1.3-2:1 (kg of food: weight growth), often depending on the farmers experience and husbandry practices.

Jade perch
The food conversion ratios (FCR) vary depending upon the level of management with 1.2:1 for fingerlings to 1.6:1 for growout being achievable. Care should be taken when feeding, as Jade perch are voracious feeders and overfeeding can occur.

I was searching for this info last night, that's why I had it handy
Silver perch info
Jade perch info

Thanks Jaymie for that thread but unfortunately that was the thread I was thinking of where someone said words to the effect of "Dr. Wilson and his theories have been much debated on this forum", something like that. I got the impression that he wasn't particularly popular for some reason?

Aaron J One of the things I am finding similtanesouly frustrating and exciting is that this is such a new field of endeavour. There is a mass of information out there but once you begin to study it you find the depth of detail a little thin. The exicting bit is that even the experts don't seem to know and even better they disagree with each other and even better still there are so many oportunities for us to contribute to the knowledge base.

In my opinion, and I could be very wrong, it seems there are two broad philosopies in the aquaponics movement. 1st there are you guys that seem to be of the general opionion that all the interactions between the various chemicals, microganisms, substrate, plant, fish and general total ecsystem may be a bit too complicated to really understand but we can work out what works and have stable productive systems. The full on scientists on the other hand seem to think that they can fully understand the working of an aquaponics system and as a consequence there systems tend to be more complicated in their design and management as they attempt to fix various "problems" (solid removal for example).

I'm I completly off, half right, a bit right or just waffling. anyway I'll be seeing Food & Fish today as he has invited me over to look at his system.

Stuart

I'd also had the same idea of fish poo being part of the diet for my yabbies.

hey stuart i recon you're half right IMHO a major problem is that scientists seek to fully understand a PART of any system and try and replicate it (which they do well), but sometimes ignoring what may seem an "insignificant" part and end up creating a complex system that was better by design the way nature did it

i completely flooded my bed above the gravel level (i was bored) yesterday arvo, i looked closely and saw many little critters skitting through the water............ i'm sure they play their part............was it monya that once told me of an alternative pond contruction method that gave up half the pond space to straw and sticks yet doubled the fish yeild due to natural food being available frm what grew in the "unused" side of the pond?

What time u gonna be at F&F's? Ifi finnish work in time i may pop up and say G'day!

Stuart - it is not that Lennard is unpopular. You are correct in that the comments related more to what you are speaking about later in your post. Lennards system is very complicated and sterile compared to waht we do int he 'backyard'. He has seperators to remove most of the solids, screen filters to remove the rest, biofilters to do the conversion and then DWC for the plants. Backyard aquaponics uses a much simpler approach generally and we would argue also has the ecosystem benefits.

At Lennards facility - the screen filters need to be cleaned a couple of times a day - not something I ever want to have to do with my aquaponics.

There is of course lots of good information that Lennard has produced and can be applied to our situation. Some will not be relevant.

Hi Stuart, Yep, there's still a lot of research that needs to happen in aquaponics, and that's part of the reason I like this board so much because people are experimenting with different ideas on many different levels, with no preconceived ideas about what aquaponics is, or should be.

I guess part of the reason why there doesn’t seem to be any hard and fast rules, especially concerning the interactions between chemicals, microorganisms, substrate, plant, fish etc, is because of the variables involved with it being a natural system. Natural systems can in some cases be almost impossible to quantify, and even the experts readily agree. Dr Savidov gave a very interesting talk in Melbourne last year where he explained how aquaponic plant growth far exceeded inorganic hydroponic growth, but they didn’t know why. They tested their aquaponic water and recreated their aquaponic water as an inorganic hydroponic solution, with exactly the same levels of macro and micro nutrients, yet still the aquaponic solution grew plants faster.. Now he is going to spend the next few years trying to quantify exactly why, what it is that causes the faster growth in aquaponics.

So as the scientific community go about their work trying to quantify aquaponics, and figure out the complex relationships between the different elements of a system, most of us here seem more interested in building simple systems to feed ourselves and families.

I guess I'm a firm believer in simplicity and I think that this is more relevant with small backyard systems. Most of the academic research is focused on the commercial applications of aquaponics, and for aquaponics to become commercially viable and readily accepted, you need to have things quantified. Hydroponics is readily accepted because it's simple, and there are quantified parameters.. I don’t know that aquaponics is ever going to be as widely accepted in the commercial sense as hydroponics, because there are so many variables.

As VB said, I don’t think that Dr Lennard is unpopular here by any means, but there has been a great deal of discussion in the past about his research and findings, and how it relates to backyard systems..

Oh and Steve that was me.. If you have a pond with fish that you are going to leave to fend for themselves in terms of feed, fencing off half the pond and filling it with sticks n brushwood, will increase the yield of fish from the pond by 4-5 times because of the natural feed source you've created..

Ponds and dams can be very productive with minimal effort and no external commercial feed, edge plants around the pond promote insect activity, yellow smooth round floats in the water are an insect attractant. Float a raft out on the pond with a pile of organic matter on it and a handful of slaters (billbugs) and cockroaches, the slaters and cockies with provide a constant source of protein to the fish.. Using lights at the water surface or fly baits.. I found a great way of getting a fly attractant that will last for a long time without being too gross. Boiling up a brick, part of a brick, or any porous rock for that matter with liver in water. The liver smell permeates the rock and acts as a fly attractant that lasts for months without being too yucky..

Oops, I'm getting way off topic here....

man, keep going, this is gold!

Ok been to F&F's and am now begining to understand many things including "if it's free pick it up".

Had an excellent home brew and got to put a few more things together in my head. Thanks again F&F.

My biggest surprise was how cheap he said he ran his pumps for per year, only $30. One of the things I had been thinking of was how to keep my system as flat as possible (no towers) but if its only costing around $30, $40, $50 or even $200 a year for pumping then I am not really worried.

Another thing I had to laugh at was what F&F said about Disolved Oxygen meter. When he asked EB, EB said "if the fish are at the top of the water and gulping then you need more oxygen". Anyone from a more scientific background (me) or aquaculture background probably wouldn't think that management practice exceptable. I love the simplicity of it though.

The logic was along the lines of air pump, air lines and air stone <$50 O2 meter $600< let the wallet do the math and chose acordingly.

Stuart