Backyard Aquaponics
A place to discuss aquaponics

Stonewall,

"You may need something like a mini sump in each grow bed for the pump to sit in."

Yes mate, that's be how I'd do it. I'd like it if they were as close to the fish tanks as possible.

"I'm not sure if this is even a realistic concern, but could the water from the fish tanks siphon back into the growbed once the pump shuts off?"

I think up to a certain size you would copy standard aquaponics designs that deal with problems but as Stuart pointed out above, when it gets really industrial you're gonna have to make allowances for new problems that result from larger scaled installations.

I will have to draw and post some pictures of what the thing might look like on the ground because I think folk are having trouble visualizing it. To be fair, the flow chart jpeg I posted is very light on detail and was only meant as a primer.

In actuality it really isn't too different from CHIFT PIST except that instead of water getting a siphon trip to a sump it gets pumped from the growbed to next fishtank in the line and so on.

Charlie,

Your comment is fair enough. The Flowchart Jpeg at the top of the tread is very light on detail and was only intended as a primer on the idea. Some people are getting it but most have responded as you have saying they don't see the point. I feel the idea is worth investigating and hope people will invest the time to "get it" at least.

The tone of information has been set largely by forces outside of my control because I've been responding to other peoples comments. At the same time me and Stuart are talking about big installation issues and clouding the water,so to speak.

I will draw some paint pictures and try to fill out the detail a bit. People often appreciate an idea if they can get visual cues about how it will look on the ground.

Part of the difference is what we are focusing on. I'm less worried about upfront capital cost as long as it pays its way down the line. The cheap chinese pumps you mentioned may not cost anywhere near that may be as little as half what the lagunas would cost but the will probably only be half as efficient say 20% to 25%. At 25% efficient you energy usage will be around 8.83kw which over a year is $24,752. That is the number that gives me vapors especially since it comes around year after year especially compared to the cost of the 80% energy efficient pump which is only $7734 per annum to operate.


Well yes and no. The four node design in the original post has four heads. If they are all 0.5m and the flow rate is 1000L/hr then each IBC (in this case) is getting its water turned over once per hour. WHat is happening though is that within that hour four times 1000L is being lifted 0.5m and put through an IBC and a GB. There are two ways you can look at this. One is as just mentioned 1000L is being lifted 0.5m four times per hour. The other way is 1000L being lifted 2m per hour. As physicists define WORK (P=hpgQ) both expressions are equal. If you had the four nodes arranged on a terraced hill side the effect in terms of energy usage would be the same. Getting the system to run smoothly would be trickier as getting the cascade to work reliably would be something I would not want to do on a small scale but the pumping arrangement would be simpler plus it is easier to find energy efficient pumps at higher heads so it would be easier to get such a design to use less energy.

I'm not suggesting such a design would be better just trying to illustrate that while reducing head height is generally a good thing doing so by adding pumps and splitting the work doesn't actually help and can make things worse (from an energy use point of view).

Acknowledged. However, as long as you are not actually increasing you bioload, would it be that much more work? There would be advantages I imagine, such as grading the fish, different species etc.




This is the point I was trying to make about requiring smaller pumps or multiple drain points through a large grow bed. The volumes of water being moved, it is not as simple as dropping a pump in the grow bed and away it goes. So you need multiples of smaller pumps and loose out on pumping efficiency or you need a sump. The other point, with pumps the size you are talking, external pumps would be a massive win. Far easier to service etc.



You most definitely are Stuart




Sure, if you have a F&D or siphon system a sump is there to help manage the fluctuating water levels. With your system design in your first post you have not facility for managing changes in water volume anyway. You will be chasing the tide with top ups.




I think the reason I dont understand the advantages of your system is, it feels like you are fighting nature. It feels like there is a lot of pumping to achieve these 'tides' through the system when I dont see any advantage of it that cant be achieved with alternative designs requiring less pumping.



The talk of acre sized grow beds was purely a theoretical situation based on this comment. telonline is trying to achieve F&D type system in very large grow beds by having tides, so no sump is needed.

All'

This post is to try and flesh out some of the detail on this type of system.

The attached paint file show a six node system with each node being single growbed and fish tank combination.

In operation the system is very similar to the CHIFT PIST systems in that water onerflows through the fish tank's Solids Lifting Overflow into a growbed.

Where this system differs is that when the growbed becomes full of water instead of triggering a bell siphon and being siphoned into a sump, it triggers a float switch that starts a pump in the growbed.

Now that the pump in the growbed is running it pumps the water from the growbed into the next fish tank in sequence of nodees and when the first growbed is empty the the float switch turns the pump off. In the pictured system each node will go through the same sequence until tank six overflows into growbed one and the process starts over again.

How much water is in the system?

The system must contain enough water to fill all the fish tanks to the point that if any more water was added the Solids Lifting Overflow would begin to flow. In addition the system must have sufficient water to fill one and a half growbeds. This amount is required to trigger the next growbed's pump float switch in the sequence.

Is it better?

Since most backyarder don't want or need multiple tanks it wouldn't work for them.
As a system for growing plants, it offers no advantage over a bell siphon or timed flood and drain.

In a system with three tanks and growbeds or more then it can allow you to do away with siphons and sumps.
And that is all it does.

If using this system a flood and drain type system can be built on the ground as it does away with the plumbing below the growbed.
Because of this it scales up to very large sizes that would make siphons difficult and sumps enormous.

Is it worse?

Much has been made that it requires a pump for each growbed but in truth most installation of more conventional systems utilize a pump per tank so it's no worse really.

Because the systems nodes share water, diseases present in the water will spead though the whole system

Where this system is worse is it requires some way of turning the pumps on and off. At its most basic you would use float switches and that adds an additional point of failure. To many this would be unacceptable. There may also be a reduction in pump life spans due the on/off nature of the system

Any other benefits?

I does allow nutrient load to be spread across multiple tanks so in a situation where you have fingerlings in one node or have harvested a tank of mature fish, nutrients will still pass through those nodes.

Its main benifit is it scales well as the system is fundamentally the samw whether growbeds are ten square feet or ten thousand square feet.

How would I use it?

Regardless of size I would use it in sets of three nodes. This keeps fish tank water retention times shortest and limits disease outbreaks to three nodes.

In my opinion, if you are trying to grow commodity crops like corn, rice, soy, etc. with aquaponics the best way to go with little upfront capital costs would just be to have a drain to waste system into your fields of crops. Capture the solids from your FT's in your settling tanks/suspended solids filters and aerate them in a large vat and proceed to pump the decanted water out to your crops. No upfront costs on gravel, not spending nearly the amount you would on pumps, and no need to worry about your GB's overflowing, etc.

Now if you're looking to grow retail items such as lettuce, kale, herbs, etc. then I think there is no better method than a DWC floating bed until proven otherwise. Cool discussion though even though I'm with Charlie and don't understand most of what's going on.

Sam,

Fair comments,

I would just say that aquaponics has the ability to do agriculture with fractions of the water necessary of conventional methods. It also retains nitrogen within the system so it doesn't come with the associated run-off presently ruining our waterways.

Demand pressure on fresh water resources and rock phosphate deposit shortages will tip the financial equations on their head. People will be looking for solutions and aquaponics will be part of the solutions. If that happens, they will want aquaponics at scales larger than than sumps and siphons can deliver.

Site selection for such a large installations can take advantage of land largely unused presently for agriculture or even habitation such as deserts or highly toxic sites.

As well as this, other options will open before us. For example, wastes flue ashes that are presently dumped in landfill will become resources ,as LECA demand skyrockets. Worm and BSF farms would have virtually unfulfillable markets for their worms and larvae products as feed alternatives are developed.

Is this the very best solution to growing salad greens?...perhaps not at present.
Is this system idea worthless?....I don't think it is. Turning deserts into farms liberates arable land to pastures for running live stock delivering cheaper animal protein to the masses as the need for feed lot protein decreases.

Its my hope that people will ask, "What can aquaponics do for us?" I think the answer is a lot if it moves out of the backyard and is integrated into the mainstream agricultural streams.

This idea may help facilitate those synergies. To dismiss it out of hand may be a mistake when all people need do is invest some imagination. The road from here to there is paved with ideas.

I just thought of something about the relative costs of GBs and FTs versus IBCs

The $/m3 I was givinng to compare IBCs with custom tanks were calculated using a top quality liner that is $20/m2.

If you did the same calculation with EPDM ($10-12/m2 (wholesale)) then it would be considerably cheaper, with LLDPE cheaper again at $5/m2 and with PVC $2.5/m2.

That would make the it $42/m3 using EPDM.

you could make all the fish tanks and grow beds equal height, Aerate your fish tanks, constant flood your grow beds and use one pump or air lift pump to move water through the whole system.

Less power, less complexity, less chance of failure.


A common problem people have is their one pump dying and they lose fish to poor water conditions. If you have any one of 4 pumps or 6 pumps you just increase the risk of a failure. You are using more power, more chance of failure and no gains.

Not necessarily less power.

There has been some good work done in the waste processing industry on the ability of FnD gravel beds being able to process more waste per KWhr than mineralisations tanks.

One of the major reasons I think GBs may have a place in AP is there ability to process more solids per kwhr. When the GBs are drained the biota in the beds will still be "eating" the solids and will be drawing their oxygen from the air instead of the water.

Brian,

Yep absolutely you could but some species of plants don't like wet feet while others absolutely thrive under such conditions. My guess is that a mix or targeted application of the grow methods is the future..

Stuart,

At really big scales I think even the cheapest sheeting options will become impractical. At this point I'm looking at some type of pinned down open weave geo-textile with a bitumem over spray as the waterproof component of the membrane.

It's interesting I was looking at PVC and EPDM prices, just this morning, for the backyard test build. I want it sufficiently tough so it will not be punctured by the media as I'm walking around tending growbeds.

The space efficiency is excellent. For the growbeds I will be boxing up three contiguous rectangles. Virtually every centimeter of Green house will be available for planting.

I've looked at a lot of spray on liner options and they just haven't stacked up. There was one operation that did but their machine blew up and the supplier of the machine and product wouldn't fix it so they closed the business.

PVC is cheap but I would seriously recommend not using it. First of all the health implications, second it is no way near as reliable as I would like (personal experience).

For comparison purposes check out http://www.geoffmiller.com.au/ They are the people I got the PVC liner prices from and they are very good for cheap GH coverings (best I've found). They may be doing EPDM now as well, although I'm not sure.

Less pumps would definately be less power but a power draw comparison would need to be made on 6 small pumps compared to 1 big pump over a complete cycle time frame. I think 1 pump would still come out on top for all three reasons bcotton mentioned.

It would be interesting to see results from KWhr mineralisation between FnD media beds and mineralisation tanks. Mineralisation tanks would require aeration so there is that power usage but how often and for how long to get maximum waste processing, theres also the additional labour/monitoring systems to achieve this. A FnD bed doesnt require any of this but Id like to see at what rate a media bed processes the wastes.

The figure I have from a waste processing manual was 473gO2/m2 with an electricity usage of 0.18kwh/m3.

This compares with 0.76kWh/m3 for mineralisation tank.

However, having praised the efficiency of GBs remember that the figures are very installation specific. A shallow GB will use less electricty than a deep one. A deep MT may or may not use more electricity than a shallow one. Like all things AP "it depends".

Stuart,

I would want as much bang for the bucks when it comes to growbed membrane but I'm pretty sure absolute integrity would be impossible so options could be considered. Just like we see on our own systems bio-slime can heal most weeping issues.

When it comes to tanks I would definitely go all out for membrane integrity. I'll definitely look at the web site as it's an issue for me right now.

Charlie,

I'm not certain myself about the best way to move the water. Do you go one big pump or would combinations be better, who knows. After the initial be flood I think from a fish perspective get as much water moving as fast as possible and taper off as the growbed empties, might be the go. For my home trial I'm going with single pumps and baki shower for safety.

When it comes to mineralization, what I know about it could be written on a post it note. I'm really a blank.

I'm inclined to towards conservative fish to GB volume rations and worms if that is the only method of mineralization. At least if it's a big system you could regulate feed rates for some addition control. Other than that size is gonna be your friend unless your forced into a water change then all bets would be off.

All,

I've made it pretty plain in the past, how I feel about air, pumping air would be my last option.

Concerning construction of the Imaginary Giant System,

I think I'd go with lined turkey nests for the tanks and use the spoil as material for the growbed bunding.