Backyard Aquaponics
A place to discuss aquaponics

Sorry, but no we don't recommend a 1:1 ratio....

The "old rule" was always 30kg .... with a 1:2 tank:grow bed ratio....

This got bent to 30kg with a 1:1 ratio.... and then further compromised to 60kg with a 1:1 ratio etc etc...

Which is why I've alwys tried to equate stocking to filtration... not tank volume.... and why Joel now recommend xx number of fish per grow bed...

If you start with a 1:1 ratio... and double your density, and your grow bed volume....

You're still only running a 1:1 ratio...




No... with a higher protein feed... fast growing fish such as trout... being feed heavily....

Will produce more wastes... not less....

Which is exactly what I was trying to say. Bed size is dependent on kg of fish so if you have less fish you can get away with less gbs, if you have more fish you need more gbs.

I ve seen a bunch of posts made by the experienced people on this forum saying that 1:1 ft:gb volume is fine as long as the stocking density is sized appropriately, ie 50%.

Possibly and I did acknowledge that possibilty further down in that post that you have quoted.

You do raise a good point though. That the ability of a systems filtration to cope with a given mass of fish is dependent on the feeding rate rather than the density.

After all you can keep many kgs of fish with a small filter be gbs or whatever as long as you dont feed them too much.

This is real problem when it comes to designing commercial gravel bed systems because we dont know at what rate Tom Speraneo fed his fish and even if we did as you have pointed out he was stocking tilapia.

Something I want to point out is the crossovers in this disscussion. Supplying enough oxygen to the stock is one thing, sizing filters/gb is another and available growing area is a third. While these are related somewhat they are seperate issues.

The fact that tilapia are a fish that can handle much lower levels of disolved oxygen than other species dosnt matter when we are talking about filtration requirements. Sure when we are talking about oxygen requirements density is a big deal and yes most fish need more oxygen than tilapia so if you are going to keep trout or cod above a density than can be handled by aeration then you will have to be injecting some form of concentrated O2 but it dosnt necessarily follow that you have to change the filter requirements. The required filter capacity is as you mentioned dependent on feeding rate and the % of solids produced at that feeding rate. Unfortunately I dont know of any one who has data on the ability of gravel beds to deal with dilute solid aquaculture waste. The papers I have found deal with treatment of sewage, greywater, parlour waste (dairy), piggery wash down water, etc. The waste they deal with and the way they load them up makes translation of their data to our application a bit tricky. In fact apart from their hydraulic design information their information was interesting but not very useful.

Yes you are correct, I visited their farm last year and mentioned AP to them, with their response being "with AP you can't get the the best of both worlds, to drive the fish hard you need the PH in the high sevens and for the vegetables the low sixes" . I don't know whether they have actually tried AP, but they are certainly successful on the fish side of things.

All true Stuart.... but you do need to bare in mind both your feed rate and bio-filtration... have a direct oxygen requirement.... on top of any need for fish respiration..



Why not use Dr. Wilson Lennard's "sizing" tool as a starting point..... when you crunch your numbers... I think you might be surprised at the result...

Ok, I have a couple of points regarding some of your posts above guys...

1. Youve gotta love the dairy industry that call their waste 'parlour' waste (but I digress)

2. Regardless of oxygen Stuart, I doubt you could stock cod or perch at the same high density as tilapia if using only the minimum filtration requirements suited TO tilapia as they can thrive in much poorer water quality - where our native finfish would start developing gill and associated disorders... so you still need adequate filtration to suit the species you are growing.

3. In commercial systems, you need max growth and production of your fish, so discussing adjusting feed to match GBs shouldnt be a consideration... you need to plan your system to be able to handle the feed requirements for max production of your fish or its not worth doing (only my opinion).

4. Why overthink it?
If you are talking about the gravel beds as solids removers/pre filters for the DWC beds, then start from there... and see how well it works

If you need it, add solids removal before the gravel beds and either use them as Duff suggested, or digest them and return if required... the best thing you can do is factor it into your plans and work out how to deal with the solids if and when you need to... its not an all or nothing scenario is it?...

Aquastud, Yeah, the AP component they have is a hydro add-on and from your post they must tweak the pH as well as the nutrient when running through their greenhouses.... man, would love to go there one day... especially once the expansions are all done - have the finished the restaurant with the moat built in yet? I reckon thats a cracker of an idea... might just nick that one

Yes, according to their website http://www.tailormadefishfarms.com.au/
When I was up there June last year it was almost complete then, along with their fresh produce building, I reckon they may do better out of these than the fish farm in the future?

Had a look at the web site restaurant link earlier and it looks great.

Value adding is definitely the way to go if you can do it... its what we are hoping to do a lot of in future.

Good luck to them I reckon

Not so much a matter of luck... but ten years+ of committment... and over a $million... probably more like $2million....

Back to the opening statement/questions. Any discussion and 'answers' provided will be based on assumptions, and without context these will be only be applicable after extensive customisation to suit individual circumstances. At best all that can be achieved is the 'discovery' of guiding principles, and these are already out there.

That said the biggest problem with RAS is it operates from a single bottom line perspective. Most (probably all RAS in fact) would fail a triple bottom line audit despite being marginally successful financially. Given that our world is moving towards putting a price on "externalities" or ecosystem services, it would be foolish not to incorporate these into any business plan or discussion of AP's long term viability.

As has been pointed out by earthbound and others, when spending the amounts of money required to make a commercial venture fly, it would be best to consult experts; however these experts don't exist for commercial AP, which is much more complex than RAS. Then couple this lack of commercial AP expertise with a triple bottom line approach and you are in very new territory. In short you need systems thinkers with AP and business experience, and these simply don't exist yet.

So my advice for any new commercial system is to DIY and start thinking in wholes; total energy audits, whole of life costs, closed loop systems, zero waste systems and so on. Yes the system must make money and be economically viable, but realise too that economics is a subset social construct of human activity, that is in turn a subset of the social and natural environment within which we live.

I meant good luck with the Restaurant/Produce Centre they had opened, as it is a very different animal to wholesale production for market.

I am thinking the only really successful Aquaculture is sea cage farming followed distantly by dams than RAS?

I assume by successful you mean making a profit? If you mean not stuffing the environment at the same time then probably dams followed by RAS then sea cage, but depending on the variables RAS then dams, then sea cage.

I havn't used the tool I thought there was a reason but I couldn't remember what it was.So I went back and tried to plug in some of our numbers. It didn't work. Because all the fields are locked even the sizing of those fields then any input numbers that produce large numbers are not displayed. So I reduced the ft size but some fields still did not display for some reason.

I also read back over the entire thread and rereading mine and others comments on the tool reminded me why I hadn't bothered before. Now I'm not saying that it doesn't have value but it is not appropriate for our (meaning for me and my partners use) use. If I'm planning a big project why would I rely or even get input from a model that I have no way of knowing what the assumptions are or how it was formulated. Worst case scenario I make errors in my calculations and when I plug the numbers into the model they produce results that are similar enough to my results that I get a false sense of security from them.

That model is based on Wilson's experience with his systems which are run in a very different manner to the systems that Joel has successfully promoted and which most systems on the this forum are based.

True to form no thread can exist for one page without being hijacked so if there are any mods looking at this stuff may be they could separate the posts so that we could have a thread on sustainability vs density and the other posts get hived off into an existing or more general thread on commercial AP?