Backyard Aquaponics
A place to discuss aquaponics

Janet-
I think you meant 10Kg fish : 100l tank : 200l GB, the other way you're talking 2.2 lb of fish to 27 gal water to 55 gal GB

Sorry, we folks in the USA sometimes get mixed up in the conversion....

Good catch Greenedo, but still not right.

6kg fish : 100 l fishtank : 200 l growbed, which converts back to
13 lb fish : 27 gal fishtank : 53 gal growbed, which reduces to
1 lb fish : 2 gal fishtank : 4 gal growbed

I'm going to claim it was a typing error.

The sad thing is that the folks who use metric didn't catch it!

doing other things

Actually, i did (the 6kg).............. but i just thought that fish swum counter clockwise in the northern hemisphere possibly somehow modifying the golden ratios LOL

I thought it looked odd, but didn't know what for

Steeve Said on another thread



Remembering that I'm the novice but it seems that you can have gravel any depth (but greater than 300mm?) depending on how your designing the system. NFT and Floating raft need to have the solids filtered from the flow so having all your gravel in one cube would work for these techniques as long as the flow, nutrients, and solids were being distributed evenly throughout the bio filter.

Alternatively you could have a system with double depth gravel in one bed and floating raft in the other and still maintain EB's 2:1 ratio.

Stuart

This might appear twice because I posted it a while ago but it dosn't seem to have come through.

Thanks Janet thats more along the lines of what I was after but not quite.

The ratio I was after was something (kg of fish, g of food?): 8 to 9 liters of gravel: x m2 of canopy.

Still can't find it but I have found a whole stack of other ratios which were interesting. However the more I think about it the more I think I just have to relax, back away from my science inclination and treat this entire adventure more as an art rather than an experiment.

Just say I could find that ratio it may be completely irrelevant to my system. For example waste produced by cweeture is going to vary based on species and quality and quantity of food that they are being fed. Quantity of substrate required will vary depending on the surface area of the gravel, ie compare bluestone with scouria. Canopy will depend on species of plant, temprature, quantity of Photosynthetically active light and proably a bunch of other stuff. Any ratio is either going to be a very general guideline or have a large margin of error. In fact the more I think about it the more complicated it gets.

So I'm going to become an adept in the intuitve art of aquaponics and be satisfied with the golden rule of about 2:1.

Stuart

I still want a temperatue data logger and a disovled oxygen meter

start saving Stuart

we ALL want a DO meter

thing that you gotta remember about the grow bed area is that the litre volume was based on 300mm AND (this next bit is important) it not only gives the bac. a place to live, but the plants a place to grow. (and also a voulme for the solids to accumulate in that is big enough to hold them with out clogging while they are broken down)

the bac will colonise any wet surface area (volume), the plants density will depend on the SURFACE AREA.

AP depends on

1) fish producing ammonia

2) bacteria converting this ammonia ultimatly to nitrate

3) the plants removing the nitrate

We aim to have a system with all three balanced

IMHO the volume for the bac. in a grow bed will be more than enough.

I think what the grow bed litres ratio aims to do is provide space for enough plants so that they can uptake enough nitrates. Otherwise we're back to a standard aquarium deal where nitrates will gradually rise and nessesitate water changes.

Bear in mind that to my knowledge EB came to these ratios by LOTS of emperical trial and error, and are a safe bet for people to work with.

Lets not get bogged down with EITHER mandating their usage OR chucking them completely out the window.

I personally like them, ESPECIALLY if you use the "weakest link" as the basis for your ratio (explained elsewhere)

Obviously there is alot of room for movement especially once we start getting into nft and dwc additions to standard gravel beds.

Oh and for the record, my preference is to have a gravel growbed AP setup and then expand with nft or dwc.
Steve

Got a table here from:

RECIRCULATING AQUACULTURE SYSTEMS MINIMUM STANDARDS FOR DESIGN, CONSTRUCTION AND
MANAGEMENT Hutchinson et al 2004

Ok cuting and pasting didn't work so to summarise. Columns are different systems.

Filter Size (m3)....13.8.......24.............8.........10-12.....4
Fish kg/pa............20t........10-14........3..........10.........10
Flow (%vol/hr).....1500......200...........450......110........50
ratio kg/litres ......1.44........41...........0.375.....1..........2.5
of bio filter

I did the ratio from the figures supplied and it assumes that their system could hold their annual production in fish all at once. Thinking about that now thats not a very good assumption

AP System has a ratio of 2:1 growbeds to fish tank columns are 1kg/25L and 1kg/50L

Filter Size (L).......50.........100
Fish kg/pa...........1...........1
Flow (%vol/hr).....?...........?
ratio kg/litres ....50...........100
of bio filter

Wow thats some difference in the ratio of filter volume to fish volume. The assumption of assuming those systems were fully stocked may through things off a bit but not that much. If it takes them 6months to get a crop of(cweetures) to market size then we could double the ratios to compare with an AP system. Thats still a huge difference.

So Steeve you were right its not the area of bacteria habitat that is the ket desgin criteria. Aslo explains why some of the commercial operations seem to have such small bio filters relative to tanks and growing beds.

It might also explain why these systems have such a problem with solids (ie Wilson's where the filters need cleaning several times per day).

I think I'm starting to get my head around this stuff. Understanding that clears up something else I'd been thinking about. Bacteria do best at around 25c (apparently) and I'll be operating my system at well below that almost all the time. If the bio mass of bacteria living on the gravel has taken up all the bacteria resisdentail space and that bacteria population is not converting AMMO to nitrate very fast because of cool temperatures this may have been a problem. Espeacially since the trout will be very hungry and polluting around 12 to 15c. However since there will be masses of bacteria habitat relative to AMMO load it won't matter if the bacteria is only operating at 50% or 25% or less efficiency.

Following on....I 've heard that AC systems can have regular problems with blockages due to bacterial growth. I'm guessing that this shouldn't be a problem in AP systems due to the large living space provided by the 2:1 rule?

Having lots of fun now,

Stuart

glad you're enjoying it, thats what its about.

yeh, solids is a bone of contention thats why gravel GB's do soo well.

I guess i was just trying to highlight the multiple functions of the gravel and each of the key areas (ammonia/bacteria/nitrates/solids) that come into play and all have to be balanced for a sweet system.

And thats just the MACRO stuff! god only knows how many micro tings are going on that we have no idea about, but i think its been prvven that if you keep the macro stuff happy the micros things go about their business with us oblivious to them and their role

I'll say it again.......solids good no big monya corn or EB tommies without them

BTW 25C and around ph 7.2 best for bacterial establishment (quicker) after that cooler temps still work fine.

Lots opf info in the useful info section, have a read.

Happy AP'ing

I've been reading Joels book and I noticed that his big system dosn't have a 2:1 ratio of GB:Tank.

If the tanks are all the same diameter and the fish tank is 90cm deep and the GBs are 30cm deep wouldn't you need 6 GB to get a 2:1 ratio not four?
Currently thats a ratio of 1.3:1.

Am I looking at this wrong? Is the ratio not volume but meant to be surface area?

have a read of joels system in the members system thread. There he states that his system is running at a 1.5:1 ratio.

It been mentioned lots of times before, and i think in this very thread, that you can down size the number of fish in relation to the other two ratios. I went into quite depth explaining it.

use the lowest of the three (fish kgs / water volume / bed volume) and work out the ratio according to that.

have a read back through the thread. if its stashed somewhere else can some one link to it please?

Steve

Thanks Steeve,

I've read your posts on calculating stocking densities and production capacities of systems based on the virtual fish tank of a system. Clear, informative posts that have helped me really understand the dynamics of whats going on in AP.

I've also read Joels thread on his system and yes he states that he has a ratio of 1.5:1 (THink it might be in the book as well). When I first read that I was really surprised and hence my reason for doing those cacls and posting that last post on this thread (I tried to do it on EB thread but its locked). I've been known to get some simple stuff wrong before but based on my calcs his ratio is actually 1.333:1. If he had 5 GBs then the ratio would 1.666:1 and if 6 GBs it would 2:1.

I guess that my real question (other than am I making a mistake) is along the lines of where did this 2:1, golden rule come from? I was under the impression from a number of sources, including this forum, that Joel had developed the 2:1 rule after a lot of expirementation and research. I also had the impression that the culmination of this research was his biggest system. This dosn't seem to be the case.

From your posts on this thread and some of my own research I have come to understand that systems that have gravel filled grow beds based on a 2:1 ratio have a massively oversized bio filter (by a factor of at least 25). There may be many other good reasons why systems should approach a ratio of 2:1, GBs:FT (not least because they seem to work better?) but if even Joels systems don't use this ratio why is it promulgated with such vigor?

Hi Stuart,
My system runs happily at a ratio of 1:1 My understanding is that the max could be 2: grow bed to 1 fish tank volume (if you want to go that far).
I personally would like to push my system that far, just to see how it goes. Now that my fish are getting some size on them I am going to add another grow bed in the next couple of weeks. I am keen to see how it all responds to the extra demands on the system. I am sure Joel is right, it could be pushed to that (two to one) if you wanted to.
I imagine though, at that ratio, you would have to manage your system very closely. I have found 1 to 1 to be very comfortable to manage.

Murray