Backyard Aquaponics
A place to discuss aquaponics

Bloody edit time out!

Let me give you a question then.

I have a 5000 Litre fish tank.
I have 10 growbeds hanging off this tank.
I stock the tank with 250 - 300 fingerlings (Trout, Barra, Black Bream, Silver Perch)

Am I at a high stocking density?

Can I do it and what are the pros and cons.

Lets add another 5 beds and up the stocking density to 375 - 450 in a 5000 Litre tank.

Do the Pros and Cons change?

Does the effort increase (obviously it does on the plant side, but does it for the fish)?

Assume BYAP Grow Beds - therefore 500 Litres of Filtration. And lets not get into the requirements to sell to public etc just yet.

Tilapia buttikoferi is not on the noxious list.

Would this be a viable species in Aus?

30kg/m3.... maximum... as above in several posts...

This is considered a medium, towards high, density in RAS operations, especially in Australia....

With complete, or close to solids removal... you might be able to push towards 50kg/m3.... but you'd need some big external filtration... and as previously mentioned, probably direct oxygen injection....

Other than perhaps WA... all cichlids are now declared noxious...

WTF?

So some CONS would be extra setup and running cost for solids removal and 02 injection.

Yes... you have 5000L of grow bed filtration... which is only equivalent to a 1:1 ratio...

The problem with quoting xxkg/m3... ala aquaculture systems... is that such RAS operations utilise external filtration systems.. sized to the feed rate... and solids removal...

In aquaponics, as the grow beds perform the functions of solids capture and bio-filtration... anything close to 1:1 is borderline IMO...

Even with the amount of grow beds you have... 250 fish is an absolute maximum.... and on the edge IMO...

And worked on the AQ formula.... you're stocking closer to 50kg/m3... which is a high density...

Your oxygen demand for

fish metabolism
feed to protein conversion
nitrification

Is I would suggest.... nearly critical... especially at high temps, and with a maximum feed rate...






Not really... adding extra filtration certainly helps... but additional stocking, with addition filtration and oxygen demands... just puts you back to where you started....

And oxygen is the key at those sort of rates... even if filtration is adequate...



Yes.... feed rates increase... oxygen demands increase.... and around those levels, if you have any external filtration... then maintenance increases...

Yep, and significant costs as well....

I feel a little loathed to pose this question but I hope that it's taken in the context it's meant, and not in any personal way..

Why on earth would someone engage a person with no relevant qualifications or real experience, to design a big RAS system, when there are plenty of well trained and experienced people out there with vast experience and knowledge who have installed and studied many of these systems for many years?

As I said, this isn't meant to diminish you in any way Stuart, but man, if I was investing a huge amount of money into a commercial project, and the vast component of the system is a RAS, I'd want many years of relevant experience behind it.

And I'd suggest a few years of experience in RAS operations, and fish keeping in general... would be a requirement as well..

+ 1

Rupe said:

P.S .... I hope you realise that this venture will require two people... full time, 7 days a week...

Plus casuals.

I wouldn't have said that there was a pissing contest going on but I would agree that the thread has been hijacked.

With the more labour as a con there will actually be less labour per kg of fish.

I quoted those figures to demonstate that ~35kg/m3 wasnt a hard and fast point to base a definition on.

Fortunately im not doing this by myself. My business partner is the Ras and fish guy. After all I did mention that it was him that had to convince me that high density was the way to go.

Also we have had a number of Ras consultants talk to us offering their services. We didnt feel that any of them wanted to work with us to develop an aquaponics design incorporating ras technology. Rather they wanted to sell us a ras system to which we would some how add a hydroponics system.

Now if any of them see this then id say to them that we as customers didnt feel we wanted to purchase what they had to offer. Dosnt mean they dont know what they are talking about but does mean that if they do then their sales/communications skills didnt proove sufficient on the day.

However having said that some of the remarks where "what we need in the aquaponics industry is someone with a lump of cash to make a leap of faith so that the rest of us can folloe along behind." and "you cant have worms in your system thats a sign that your bio filter is about to crash".