Backyard Aquaponics
A place to discuss aquaponics

I found all you wrote very interesting. Thank you TCL. I am increasingly convinced of the superiority of AP over HP. I think there must be many inputs in AP that we don't even know to measure that give the system when matured a more well-rounded balance of nutrients.

Please forgive me for asking again... The question I keep asking but not yet answered.... or I am just not getting it! .... is EXACTLY what that factor in the 2:1 ratio stands for .... the 1 is for volume of water in Fish Tank..... is the 2 for the volume of water PASSING THROUGH the growbeds? (40% of GB size)... or the actual volume of the GB... its volume before any media is added... the size that is to be built. I would like to design with this strongly in mind for the reason you state below....



I want equilibrium to be reached as soon as possible. It would be the best use of the space and money I will be investing. Especially as I will move on to the next unit when the first is doing well. I understand now.... eventually! that the extra water for the fish is not a problem as long as I don't overstock beyond what the filtration system can handle. But why waste the fish tank water either? I already have the desire for the buffer of extra water met within the design because of the sump and top flush tank.

I now want to get close to that true 2:1 ratio in terms of build to maximise everything straight off. There must be a reason it has become a guildeline... I accept that it is just a guideline... but I want to use it as a guide from design stage. But first I need to understand what that factor stands for.... just actual GB size? ... or the amount of water flowing through (which is 40% of GB size once you minus the 60% taken up by grow media)

It's total growbed volume (media+water)
Right now I'd recommend 1:1 with 3kg/100L max. That seems to be how the most successful backyard systems are running - not sure if I'm right in that assumption though. There's a poll somewhere on the forum....

Thanks Steem!

The way the ratio works is:

1000 litres of fish tank fully stocked @ 6kg / 100 litre of fish requires 2000 litres of growbed volume. This can be difficult to achieve in a backyard system.

It would probably require around 4000 litres of water to be transferred through the growbed per hour to keep the water clean though.

Most people have around 1000 litre of growbed per 1000 litre of water, this is easier to manage.

Sorry, thought the 40% question had been answered earlier

Since you have a very large volume for water in your pond, I wouldn't worry too much about the "ideal" size of the growbeds. Start with what you can do, and then as the system becomes more mature, you can look at expanding if you want, or just setting your stocking density appropriately.

The 3kg/100l for a 1:1 system -vs- 6kg/100l for a 2:1 system works out to the lesser of (6kg/100l for the tank) and (3kg/100l for the growbeds)

For example:
Your pond, I believe is 7000 l, that means that if you start with 8000 l for your growbeds; in a mature system, you can stock up to 420kg in the pond, but the growbeds would only support 240kg of fish on the filtration side. Therefore you would only want to stock up to 240kg of fish.

If you later add another 8000 l of growbeds, your growbeds would be capable of supporting up to 480kg of fish, but your pond would only support 420kg, so you would be limited to 420kg.

Getting too hung up on the ratio can sometimes lead to confusion.

I think that most people would agree that if you are going to overbuild, it should be done on the fishtank side.

the 1 stands for FT volume
the 2 stands for GB volume

Greenedo, your example is exactly what I do have in the current desgn..... so I am going to take everyone's advice and leave it just like that. 7000 litres of pond water filtrating through 8000 litres of GBs. I will watch my fish stocking rate. I want to thank everyone for their help. Much appreciated!

I love reading your questions C
...it is showing me how much some of us have taken for granted
...it is also pointing out a few things I didn't know too

keep them coming

+1 for what Ellkaybee wrote:

keep them coming, Chelle

frank

Questions I am NEVER short of! It is the patience everyone has in answering them that is so special here. Especially when in my inexperience I just don't get it at first. This forum is my most favourite on the net.

hi all, just wondering why so many of you guys use expanded clay balls and wondering what influence this has on the rules of thumb that are being discussed
I presonally like DWC methodologies as you dont need to clean or maintain gravel/clay balls, plus i've found in the part that any maintenance that does need to be carried out, often causes idsruption of the anoxic layers and resulting in nitrite spikes.

i'm building a couple of systems that are with 5500 ltr fish tanks, (three tanks for stagered harvesting and grading (for optimal growth), then DWC volume of 8000lts with a total system volume of around 16000 ltrs, and plan to stock to 200-240 kg.
i guess this and the rules of thumbs are within these boundaries, but i wonder the implications of DWC rather than clayballs (sounds like an experiment in the making!!) certainly less bacterial surface area, but i used netting in the second stage filter for fine solids and bacterial breakdown, (prior to degassing) - see below

agree potassium and iron often lacking, but iron chelate and KOH would sort these out, base addition tank easy to incorporate into the sump systems.

best wishes from a suprisingly sunny scotland.....

the filtering system you propose is is an interesting new subject, Charlie
so I think you should start a new thread,
easier to refer to later on

Frank

what are DWC channels?

Clay balls are the media of preference in growbeds Charlie due to their weight, although cost is greater than pea gravel.... but these are "flood & drain" systems... not DWC...

And hardly anyone has ever bothered to clean the clay balls... unless they're moving or substantially rearranging their system.... they just don't need it....

And flood and drain growbeds usually don't have any "anoxic" or anaerobic "layers"....

That's the beauty of them.... what made you think otherwise...

Oh, and we don't filter out solids.... we like them .... (see below).....

Other than that.... your filter (drawing) will work just fine.... absolutely standard stuff....

Can tell you've spent some time at UVI.....



Are you doing DWC in raceways... ala UVI??....

And are you suggesting that DWC raceways have less bacterial surface or clay balls???

DWC - Deep Water Culture

plant roots suspended in oxygen saturated water/nutrient solution, gives possibly the fastest growth (second to maybe aeroponics)

"dutch pot" style is a planter filled with media stuck in a bucket filled with water.

use the search function and you will find many posts that discuss DWC