Backyard Aquaponics
A place to discuss aquaponics

OK. I've always been a bit of a Maverick and I cracked this Aqua thing without any existing concepts of how it's done I had a few ideas on applying deep water culture and they worked. What this means/gives us, is another frame of reference, and a good one for small systems, my prototype being 150 litres.

The 1 kilo of fish in 600 litres approach was only this - I had a pond, hell, throw some fish in ASAP and get the ball rolling. And it paid off well in that I'm getting great growth in a 50 litre bed. I didn't have the parts for more beds or the cash for more fish at the time. It's early days yet.

I will stock this 600 litres with up to 18 kilos of fish eventually. But the ball is rolling, and I have 600 litres of Aqua water, very successful experiment... I have tomatoes corn basil miniature squash and cucumbers in the bed. all young'ns, growing fast.

The key to many breakthroughs I had in deep water culture was water circulation. It didn't seem to matter how much fish I had per volume of water, but whether the plants had adequate access to the nutrients. Nutrient concentrations only mattered in that I had enough nutrient to cover an alloted canopy space - being approx 1 kilo of fish to 0.5 m2 for fruiting plants. Or approx 1 lb fish to 4 sq ft.

I could halve or double the water with the same fish and canopy space and there was no noticeable difference. And now I have much more water, and no difference.

As a general rule of thumb I discovered if your plants have access to enough Aquaponic nutrient once every two hours they will grow.

My 600 litres pond goes through my 50 litre bed every 2 hours. And so it grows.

I hope I'm explaining this ok.

That bed is filling and emptying every 5 minutes.
With 12 times the fish I could then grow
12 times the bedspace requiring a nutrient circulation of only 1 x per hour.

What? You might ask. Dodgy Math!

I had to recheck too. The 600 litre pond with 12 times the fish becomes 12 times as concentrated. This means the nutrient content is only required by plants once an hour at this 'strength'.

It is using this model that will give me the ground rules for feeding beds then DWC in series before return to tank. Better filtration, twice the bang for your pumps bucks, better water for touchier species.

Another key to small aqua systems, especially DWC, is a relatively stable temperature. Buried or in a well made building.

Sorry AA, I think I lost you a bit there..... I must be tired....

That's OK EB I lose myself sometimes trying to go from A to B even if there is a connection.

Basically - The same nutrient content in 100 or 1000 litres will grow plants. The limiting factor being water circulation.

Nutrient content (fish stocking rates) will tell you how much circulation you need to ensure your plants are fed. This matters when you have hardly any fish, or want the nth degree out of the power you use.

Other contributing factors that must be addressed - aeration.

A 150 liter (39 gallon) system is virtually desktop. Fish wise, it will not support an adequate stocking density for food consumption, which is half the point of AP? As I have learned from experience, small systems are incapable of accurately replicating larger scale aquaculture. Plants and vegetables can be grown from them just fine, but I don’t see the point in AP when you can’t harvest the fish as well. IMHO, small scale systems are best left as hydroponic systems, or AP systems without the food fish side of the production.




This is promising and has opened up a theory that I had previously no evidence to hypothesize. My hypo is this: The smaller the system, the greater the gain in concentration of nutrients provided by the same ratio of fish in a larger system. Anyone care to elaborate or discuss? Initially I was surprised by the light stocking ratio of your system AA, but now it is making sense. In a larger system, the nutrients get spread out and it takes longer to get nutrient levels high enough to provide for more growth?



“Canopy Space” is a fuzzy measurement to me simply because the variables lie in the type of plant, fruit, and mass of the “canopy.” I equate water circulation to aeration and where you have one you have the other and vice versa. I aerate my sump tank with floating raft and leafy plants do well. However, they get the runoff from the gravel beds and therefore less solids and more NFT effect, which is not sufficient for tomatoes and the likes. I can grow fruit in my gravel beds though.




I attribute this fact to the small scale of your system, no offense meant. I think it doesn’t take much to nitrify the small amount of water you are cycling, and due to it’s limitation on nitrogen capacity, doubling it doesn’t change much in the way of supply to the plants?



“much more” is a relative term. How much more?



Again, within your system that is an adequate watering time. For a larger system cycling the entire head tank volume through grow beds at a ratio of 600:1 would be way too much watering. Back to my hypothesis: a larger system must get closer to the ideal stocking density in order to have successful plant growth. Thus advising Jamie on whether or not his tank is too big is relevant. He needs to be aware that a large tank and system will have much different effect on his results than a small system.




You are fine, I just hope I am not being too difficult;) and explaining myself sufficiently




Yes on everything until you backed down on the watering times. In a small system, letting your fish sit in 12 times as concentrated waste 12 times as long will probably result in mortality. Just a guess.




I agree that DWC in series with gravel beds makes good use of emulsion. That is what I am doing presently. I encourage everyone to go with the hardiest species of fish due to the high demands of recirculating tank culture on fish mortality.



Agreed…climate control is a must.

How are we doing so far???

Yes and No. The larger the system, the higher the stocking density must be in order to achieve the same level of nutrient saturation to overcome the increased buffering capacity of large bodies of water. Therefore same fish to liter(gallon) ratio used in smaller systems is not applicable.



..and stocking density, and volume of system that is buffering the nutrients, and the amount of grow space you are moving the nutrients through, and the type of plants your are growing (demand), and of course water temperature...DO content. All of these variables shift at an unknown degree as system volume increases.

You're making it hard hehe.

I must go to class. I'll e back later to dig into this. I think you have a preconcieved notion that everyone must grow food fish because you do - or that non edible species are not feasible for a larger system. It's wrong. If you got a market, grow whatever.

LOL -



No, No, No - All fish are game in AP and there's nothing wrong with ornamentals. When considering system size, simply consider your species and stocking density is all. Some species tolerate high density and poor water quality better than others. For a beginner, the hardier the better. Goldfish tend to be weak and fickle. Cichlids would be a much better starter. Right now I want to grow Sturgeon, but they are intolerable of high stocking densities and require much volume. Could it be done in AP? Yes. Depends on what you want to grow and sell right?

At one time or another, we all experience a fondness for the concept of Absolute Truth.

Examples of absolute truths include:

- Aquaponics means recirculating water from a fish tank through grow beds back into the fish tank. The simplest form of aquaponics is to grow a plant in the same tank that the fish are kept. Even if the plants are not grown in the same tank as the fish, there is no need to recirculate the water. The nutrient rich water can be delivered to plants without being recirculated at all. As the plants use the water, it can be replaced with fresh water.

- Growbed media should be gravel. It depends entirely on your personal circumstances and resources and what emphasis you place on plants or fish as the principal crop....and what size system you are planning. If you have the mindset that your fish tank is a nutrient factory, coco-peat could well be the best media in a well-designed, 'run to waste' fully integrated food production system.

- Growbed to Fish Tank ration should be 2:1. As this thread demonstrates very clearly, the notion of a 2:1 ratio is indicative only. The precise ratio will depend on a variety of factors.

- Aquaponics is about growing food. Who says so? It can be about money - if so, there are much more lucrative fish and plant combinations than barramundi and lettuce. It might be about saving the planet so the outputs might be Giant Kokopu and endangered native orchids. Or it might be about indoor plants and brightly coloured aquarium fish.

The problem with Absolute Truth in aquaponics (as with everything else) is that there's no such thing. There's opinions, preferences and circumstances......and that's what make the world such an interesting place. Open minds will produce a million variations on any theme....including aquaponics.

I like this thread......it dares to be different.

Aquaponics can be for aesthetic reasons as well...no absolutes

This is what I'm doing. I was under the impression it wasn't strictly aquaponics but I realised it shared the same principals of using the fish to feed the plants and having the plants help keep the water clean for the fish. So that's nice to read (not that I'm keeping fish for food, tank's not big enough).

It's making more sense this morning....

An interesting side issue to water flow rates and nutrient content is the Virgin Islands system. 30m (98 feet) long raceways with very slow water flow down one raceway and back up the next one, so the water is flowing slowly past 60m of plant roots. Yet, when I asked the question about lack of nutrient at the end of the flow, Rokocy said that the level of nutrient in the water at the end of the growbeds was the same as at the start..



I think theres a difference between absolute truths and trying to define to others, simple system design principles that are tried and tested and will work. When explaining what aquaponics is, to someone with little idea, you must give them a concept that they can grasp the meaning of, rather than say "well it's just about anything you like involving water, plants and fish".

I knew this thread was gonna be interesting (got along way to go yet to catch religion )

Absolute truth is when someone insists that there's no other view of the world.

Simplifying complex concepts to enable other people to better understand them is a good thing.

Some people learn by listening to other people's view of the world - other people learn by experimentation. Depending on your learning style, both work.

A smart bloke recently wrote something that sums up my approach to aquaponics (and almost everything else).......



Oh.....it was you, EB.

Yep.......

Exactly, that's why I'm wondering how and why you define the above as absolute truths?