Backyard Aquaponics
A place to discuss aquaponics

I guess maybe that's the reason EB has settled on a 1.5:1 ratio....

Pushing toward the max but with a safety margin in reserve....

It would seem to make sense that a 1:1 ratio could be harmonious with fish of a certain size but might begin to stress the limits of a systems balance as the fish grow.....

additional grow bed space provides the extra capacity needed by growth and allows for fluctuations in cropping densities, nutrient uptake demands, harvesting etc

Have you noticed any correlation in your water test results to crop density, harvesting as your fish have grown Murray?? or is everything to subtle to register in the tests?

Stuart, yes, my system thread is locked ATM because it's a work in progress, after I get the basic info in there over the next week or so I'll open it up...

Though you're right I have mucked up my figures a little in the listing of my system here, it is still a work in progress, I'll fix them up soon.. AlthouthI mentioned the fish tank is 2000L total volume, it is never completely full, and infact now I go and measure it, it's only 850mm high, so it's even less...

I think your probably getting a little too caught up in the whole ratio thing... These figures are given here, and in my book as examples that work.

Both the 2:1 ratio and the 6kg per 100L are figures worked out through years of trials and experimentation by Tom Speraneo, I've never claimed them to be my figures.. I've been a member of their mailing list/discussion group for about 8 years now, If you go and check their website I think there is a link there to the archives of the mailing list.. There is an absolute wealth of information there about all things relating to ratios, stocking densities and more... You can also buy their manual that has further information.....

Because Tom did the research into gravel bed systems over many years, trying many different combinations in ratios, stocking densities, media particle size, etc etc... You can find bits of his research information about the place, though it's not super easy to find on the internet, and unfortunately Tom passed away a couple of years back..

Keep reading, keep researching, and always keep in the back of your mind that, as you mentioned before, aquaponics is almost verging on art rather than a pure science in many aspects. Scientist that have been researching aquaponics for decades still don't comprehend it all.

Also remember guys that the 2:1 grow-bed to fish tank ratio is based on what Tom found was required to stock the 6kg per 100 litres. If stocking less than this then the idea is that you would not need to keep the ratio as high.

Remember too the other very important factors:

- feeding rate
- planting rate

Obviously if you are not feeding as much as you can - then not as many nutes are being produced that need to be removed. Also - if you are not planting your beds fully - then the ratio means nothing. Types of plants will also be a significant factor because some pull more nitrates than others.

As Joel says - don't get hung up on it. Use this things as an indicative thing while setting up and then monitor your own systems nitrate levels and adjust planting, feeding and fish stocking density to suit.

Adding more growbeds is hardly pushing the boundaries. Having LESS growbeds with lots of fish is pushing the boundaries, because you have less gravel to support your bacteria. By adding more gravel, you are INCREASING the surface area for bacteria to grow on, thuis DECREASING the liklihood of ammonia and nitrite spikes and thus having a much more stable system.
Yes, if you have more growbeds, technically, you will have more plants extracting the nutes, and you may find nitrate levels drop (because plants feed on nitrates not bacteria) and plants may suffer, but in turn you can then INCREASE your stocking levels an/or feeding rates, in which case your fish will do a lot more shit, and your plants will grow faster. But ONLY if you have the surface are for the bacteria colonies to convert the nasties to the good stuff.

Or of course you can just harvest some stuff and replace with seedlings or not replant that area at all until your fish are bigger and can produce the nitrates needed to support more plants.

exactly

Mmm, more growbeds equals more area for plant growth, more area to distribute solids over so that they can breakdown better, more volume for worms to grow to break down said solids...

yep, kinda what I meant.... 1.5:1 is probably safer than running 1:1 as the fish grow....whereas 2:1 might be a bit excessive

Again it all depends on your fish stocking. Remember that in essence 2:1 with 6kg per 100 litres is the same as 1:1 with 3kg per 100 litres or 1.5:1 with 4.5kg per 100 litres.

true, true & true

Spot on.

It VERY important to not get hung up on the bacteria. My personal opinion is that the growbeds often provide much more surface area than is actually required.

As Joel just stated, it the whole meal deal. Solid entrapment, nutrient removal, nutrient conversion, habitat of worms................and probably a dozen other stuff we haven't quantified yet

rupe, 2:1 is only 2:1 if it is planted out................otherwise its giving you more safety.......more area for solids, more bio-area.

Different plant are going to uptake nutes at different rates.

If you have a 2:1 ratio that is only half planted then you're only going to remove the nutes that a 1:1 bed will.

Don't forget one person may feed their fish 2x as much and there fore require 2x the plants.

We gotta be clear on the BALANCE!



Steve

Then there is also the subtle differences between fish species, and different fish feeds and their protein contents..

Knew I shouldn't have bought into this one LOL....

So many varibles, so easy to assume and/or understate things LOL

Granted... all of the above.... no harm in it being reinterated in posts though as it's central to the whole AP experiment....

Think that's the real appeal of AP to me in many ways... the holistic nature... an attempt to mirror a natural system and balance in a backyard...

... or at least as close as a mere mortal can ....

Onya Steve - been caught out not reading all the posts again mate. I said almost exactly the same thing higher on the page. Mind you repeating things is often the way people learn .