Backyard Aquaponics
A place to discuss aquaponics

First of all, I am really enjoying the forum. This concept of merging fish and hydroponics together seems very efficient.

Anyway, I am digging around and like usual, finding it a bit hard to separate to forest from the trees due to the diversity of application.

So, simply, here is the question. Say I want 1 kilo of fish per week to eat - how big of system do I need?

Now, this might not be too hard to calc because we live in the tropics. This means our temperature is very stable at about 26 C year round (plus or minus say 3 degrees).

Anyone have the number off the top of their head or can point me to where I make the calculation? We would probably grow something like Tilapia if that matters.

Welcome and maybe this link will help answer your question...
http://backyardaquaponics.com/forum/vie ... highlight=

1 kg a week depends on your grow out time. for fish that mature in 12 months you will require 52kg in your system. For those that take 6 months 26kg, and those that take 18Months 78kg.
To support 6kg of fish you should have a minimum of 100L of fish tank, and 200L of grow bed. so. simply

Fish_________Min Fish Tank___________Min Grow Bed
26kg__________450L_____________________900L
52kg_________ 900L_____________________1800L
78kg_________1350L____________________2700L

But read up on the thread Gotfish posted, it goes into more detail. But this should give you an idea of size.

it would be more effective to have a variety of sizes though right? May be a problem with fish eating smaller fish...? There's no need to have 52k of fish in the system to eat 1k of fish a week. only the fish you're going to eat that week needs to weight 1k. There's a fish in there you won't be eating for half a year, plenty of time to fatten up. I'm not saying having 52 different sizes of fish or adding a fry every week (gulp) but ya could reasonably have 2 different sizes of fish, no? Hmm.. that actually woudl be easy if you seperated your fish tanks into 2 or 4 seperate tanks... hmm. sorry thinking and typing.. ill stop now

Most growers seem to segregate their fish in age batches. So depending on the complexity of your system you might have 2, 3, or 4 tanks for 6, 4, and 3 month rotations, respectively. Some (most?) fish are cannibalistic, some aren't. Tilapia definitely are, which is why they are mouth-breeders.

I agree, but treedude asked for simplistic... I certainly plan on havin multiple batches, hence my 7 tank system design

Kuda (and others) ..... it's quite true that these are the stated "optimum" figures.... but I think it's time to reinforce some old wisdoms developed through the early days of the forum.

Lately there appears to have been a rash of people that either haven't taken the time to read through the earlier parts of the forum or have seized upon "optimum" figures (such as above) and raced headlong into the fish stock slaughter yards.....

While a 2:1 growbed:tank ratio is quoted, it is in the context of the ratio is the suggested requirement if you were/are stocking at HIGH densities like 6kg/100ltr.....

In reality with a growbed volume of twice your fish tank, you'll need about the capacity of your fish tank again during a flood cycle or some sort of "controlled" sequential flood mechanism....

Otherwise your fish tank will be empty... other than the large layer of overstocked fish gasping for air.

Of course if you have twice the tank capacity... then the ratio becomes more like 1:1 anyway..... and/or the stocking density becomes 3kg/100ltr...

6kg/100ltr might be fine FOR EXPERIENCED growers who CONSTANTLY MONITOR their water parameters and might be fine (in terms of sheer caculated numbers) when the fish are fingerlings.

I would highly recommend that people re-read the early parts of the forum and review the elder members systems....

And stock at levels of 3kg/100ltr for at least the first year while the system matures....

fair point Roz...
especially about the 2:1 and not having enough water (I have so much water i hadn't considered this...)
also the propper research vs minimal information approach, this will reflect badly on AP and the forum if many ppl build 'fish slaughter yards'.
It is my failing as an engineer that I assume everybody I speak to has an understanding and training in engineering, equal to or above mine...

Treedude.
It is VERY easy to kill all your fish and lose a small fortune.
Please read up in the forum a lot before you begin.

You should understand
1. nitrogen cycles
2. effect of algae on a system
3. Dissolved oxygen and how it can deplete or be added.
4. Fish temperature tolerances.
5. Plants, and what they need to survive, Nitrogen is not enough.

I would suggest you build a system with goldfish to try, and practise on before going big time.

All of these things are discussed in one or more articles in the first edition of the Backyard Aquaponics Magazine for this very purpose . Joel - perhaps it should be compulsory reading for new members

Make it a quiz before you get posting privildges

Entrance exam :-) hehehehe funny

Oh lord no..... not a BYAP citizenship test....

Amanda..... you still out there.....

ROFLMAO! Should we have a trade qualification or something? Make sure all new members will add to a productive society and not just jump on Welfare?

Well, I was wondering when I first posted if everyone was gone - I guess not and I didn't take into account that we are on different time zones. Right now here it is 3:42 AM - (I tend to wake up early)

Don't fear talking to me as an engineer - I am, more than 25 years experience. Mainly in software and hardware for computers, but I did enough applications for manufactoring to have some mechanical too - besides, it is all math after a while.

I have all the space I could ever want - so 7 units, 3 units, etc are not an issue. Also, if some fish get too big and I need to make room - I think I have at least half a hectare of ponds. Honestly, I don't need to raise fish, I just like the idea.

Really, my motivation is this: Here in Costa Rica I have noticed that people don't raise vegetables but they often do have tilapia. I am thinking a simple system might just catch on since they do have a pretty good education and are willing to try things.

I did read the magazine - cover to cover. Nice job!

Am I to assume the reason for a 1:2 ratio is that you need that much surface area to covert the ammonia? Since you have to keep water flowing, perhaps implementing more of a steady state system would be better (i.e. not a flood / drain).

By the way, my secondary reason for doing this is I prefer vegetables grown hydroponically and it is a real challenge to grow vegetables here due to the aggressive environment - i.e. nematodes and fungus in the ground.