Backyard Aquaponics
A place to discuss aquaponics

Living in an apartment in Johannesburg, my existing balcony system is a typical media bed system with no additional filtration. I am moving to a house soon, and, of course, my new system will have to be the one featuring all the features I have been salivating about reading this forum.

I have subsequently been doing research designing the uber system, and after some questions about filtration design, Scotty put me onto an article about mixed cell raceways. I quite liked the space efficiency of this concept, compared to round fish tanks. It does however appear to be a fairly new concept, and I would hesitate to call the data I found online on the self cleaning ability of mixed cell raceways conclusive.

I would therefore like to test the concept of mixed cell raceways myself. In the article, they propose three cohorts of fish to utilize the fish tank volume efficiently. This being an experimental setup, I would prefer to make it as small as possible.

Assuming a harvest weight of 400g, and stocking density of 20kg/m3, is there a way to determine an optimal fish tank size? Some literature suggest that the size of the fish is influenced by the size of the tank.

Your input is much appreciated.










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Hi
Can you expand a little on the design. I thought a raceway was a constant flow of, fresh clean water.

I don't know if this is the original paper I referred you to but might help explain a bit (very heavy on graphics so not really a good one for a low speed connection)- https://www.was.org/documents/MeetingPresentations/AA2012/AA2012_0287.pdf

This is probably an easier summary without the extras - http://pdf.gaalliance.org/pdf/GAA-Ebeling-Aug04.pdf

Hi Scotty. Thanks again. However, I want to scale the MCR down due to space constraints. Where I am stuck though is, does the tank volume have an influence on the growth rate and possibly final size of the fish? For arguments sake, can you grow tilapia to 750g in a 3000 l tank?

Thanks



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Thanks for the links Scotty.

Plenty more out there Bodgy.

Nicol - As far as I know (not being an expert on Tilapia) you can easily grow Tilapia to 750 gms in a tank that size and probably smaller. You need a certain volume of water per pound/Kg of fish but filtration has to be taken into account as well. The mixed cell raceways are more space efficient and in some ways easier to construct but I suspect the rules on stocking densities and filtration are no different than any other system.

http://www.backyardaquaponics.com/forum/viewtopic.php?f=12&t=6646

Keep in mind that these are maximum stocking densities based on final grow out size, and half of that would be a better way to go (even though Tilapia are tougher than most).

and here's a different one that came via Guitarwes in another thread -



I'm not so sure about the initial question regarding the 400 gm fish but that stocking density seems too high.

Hi Scotty. Thanks for putting up with my relentless questioning.

As a mild sufferer of claustrophobia, I was a bit concerned with having big fishes in small ponds, but judging by what you said, it should be fine.

Cheers


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Hardly relentless Nicol . If you're primarily interested in the plants you can stock the system on the light side and still do just fine as long as you have a good quality fish feed.



Depends on the fish, how big you grow them, and how the tank is arranged. I could have 300 gallons in a really narrow tank and I don't think the fish would be all that happy about it .

I know my way around plants pretty well, but the fishes fox me all the time. I decided to do a course in aquaculture at the University of Stellenbosch, and I am proud to say that I aced my semester exams. Unfortunately, being a mechanical engineer, I have a compulsive need to know everything, and the course can't keep up with my desired learning curve. Scotty, your links provided much relief to my insatiable demand for more knowledge, and I really appreciate that.

I have read a number of books on aquaponics, including Sylvia Bernstein's one, and everything I could find online written by Rakocy, Lennard, Timmons and Ebeling. Are there any more books or authors you can recommend? I don't like the "rule of thumb" kind of books. I want to get right down to the bottom of it.

A lot of the information online is based on a "this worked for me, so this is how it should be done" approach, but no system, whether mechanical, electrical, biological or otherwise, is ever that simple.

My balcony aquaponics system have provided me with hours of joy, and at least an equal, but likely greater, amount of frustration. I have desire to "go commercial", but I would like to develop my skills, based on proper training, research, mentoring and experience to a point where I can contribute to the AP community.





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I think you've pretty much nailed it with this statement. Unfortunately, either a lot of the information is in the hands of private enterprise, isn't available or hasn't been figured out. That's because AP as a science is still relatively new and biological systems are extremely complex. I certainly listen to peoples experience as much as to research, they are both useful. If you think about it it's better to know why something works but barring that knowing that it worked for a lot of people also has value. I'm not sure it's getting any better but a couple of years ago there were so many people claiming to be experts and offering courses or books, it was a real eye opener - most were really not experts and there were almost no successful commercial systems (there still aren't very many).

My suggestion to you is if you are really interested learn about it in more depth from those who have done it the longest or are some of the best growers, like some of the ones you mentioned (and a few others like them) and people like Ryan Chatterson who understands the process, has a microbiology background, worked for a company selling aquaculture equipment and is an excellent grower.

Dr. Nate Storey (Bright Aquaponics) has some videos on YouTube that are worth checking out and he has developed a tower system for growing plants. I think his series on nutrients in AP are pretty useful.

You can't know everything but information on related sciences like microbiology and filtration, aquaculture, plant and fish diseases are good to know at least as they relate to AP. You'll probably never run out of things to learn.

You may also find information on specific fish species and their culture to get you started. Here in the U.S. we have regional aquaculture centers that do research and publish much of this information online. So for instance something like this is what I could find for sunfish culture - http://www.ncrac.org/node/278

There is likely more than one of these for catfish or trout that could be useful in many countries.

Hi Nicol
I was a little concerned when I read you initial post.
I have heard of the power supply problems in SA. and as I am sure you are aware mixed cell raceways are power hungry.
Today I was at an AP conference here in the UK and got talking to Wilson Lennard PhD. I asked him about MCR. He said that they were originally deigned because existing Concrete trout raceways in the US were running into environmental concerns over dumping waste water.
In other words a solution for an existing problem. Not a first choice for a new design.
I came away with three words ringing in my head,”Round Fish Tanks”

Hi Titus

The power problem in SA is a big thing at the moment. We worry.

In the articles Scotty generously linked, MCR was presented as a cost and space efficient solution, which is what peaked my interest initially. The concept makes sense but I found very few references of MCR's other than one Ebbeling designed online. Round fish tanks on the other hand have proven itself many times over. Don't fix it if it ain't broke, I suppose.









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Probably either would work but the round tanks would still be my first choice.

.....you always can fill the area around the tank with peripheral stuff (filters, pumps, grow-beds, NFT-tubes) to "square up" the space...

thjakits