Aquaponics Shop - Rush Creek

[aquaponics-shop]

Recently we did a major upgrade to our Aquaponics Shop Rush Creek system.

The Aquaponics Shop controls two out-door systems of its own (Rush Creek and Nundah). We have been building systems for a couple of years now.

Our first system, Rush Creek, was designed as a flood and drain system based on an existing design. Since that time we have had good successes with it but have found the design to be problematic in many areas.

Over the last couple of years, with a reasonable amount of experience and research under out belt, we have found that the continuous flow model has many advantages, as we see it, over the flood and drain model.

We have converted a few of our clients systems and Nundah was built as a continuous flow system right from the start. Based on those successes and the issues with the 'old' Rush Creek system we decided to upgrade it to our preferred model.

GaryD was kind enough to come out and give us a hand.

As you can see by some of the photos attached to this post we did have success in terms of growing plants and fish in the system when it was flood and drain. The problem with that model is:
1. Management issues surrounding water flow regulation
2. Cleaning of gravel (don't let anyone tell you they don't have to be cleaned!)

The first photo shows some of the beds as they were a few weeks ago. Note the orange cement mixer in the background - that was used to clean the gravel from one bed every 2 months - not a fun job! Our success was based however on cleaning each bed once a year (we had 6 beds).

The second photo shows the beds from the other side. Again our success in production was fine. Note the condition of the gravel in the bed closest to the camera - it had been cleaned only a few weeks earlier which is why the growth in that bed is low (the beds must be emptied completely of gravel to clean them properly).

The last 3 photos show the fish. We have been eating them for a while now. Some people say Silvers will not grow past 300 grams in these systems - well nobody told ours that :-) We pulled 14 of them out a couple of months ago and they ranged been 520 and 750 grams.

Finally I will just give you some general information on the system:

We have one fish tank with circa 2000 litre capacity. It has approximately 210 to 230 fish in it now with an average weight of approximately 500 grams in it.

We have six grow beds. They are approximately 2 meters long and 1 meter wide. We have grown too many different things in the system to list here.

More to follow on the actual upgrade.

[aquaponics-shop]

Without attempting to lecture on building a system I would like to share some of the major points. If this information helps only one person then we will be happy with that.

Firstly, when doing any system and especially an upgrade it is very important to do your design on paper first! Check it so many times that you are sick of seeing it. Then leave it for a day or two and have another look. When you are sure you have covered all the points then start getting the parts. Even then you will almost certainly come across something you forgot!

You might think it is less necessary to do the above on an upgrade but the reason it is more important is that you have fish in the system. Hence if you are halfway through the upgrade and realize that you have it wrong you might not be able to turn back or go forward. This might be at a point were no water is flowing - no flowing water means the fish are in trouble!

A continuous flow system works with only one pump. This has many advantages in my view but I will not elaborate at this point. You need to think about how to get the water from the lowest point in the system to the highest point(s) via the pump and then how it will flow back down by gravity.

In this case we have an existing central sump for the whole system (picture 1). We can use a low 200 Watt pump for the wholes system as it is continuous flow. In this case it pumps the water up the central pipe and then the tee at the top sends it up and over to the grow beds while the other branch sends the water to the fish tank.

This raises another point - you do not have to run water from the fish tank to the grow beds and back. This is a misnomer. So long as the water is circulating through the whole system the effect will be the same! We have done tests on this very principle. In this case the water goes from the sump to the fish tank and back and from the sump to the grow beds and back. This gives us a huge advantage in that we can turn off the full grow bed system and leave the water circulating for the fish.

Picture 2 shows the original configuration of pump from the sump to the fish tank. As you can see all I did was put a tee in the top to send the water over to the grow beds as well (as previously mentioned).

Ok, so that got the water out ... now we had to get it back. In this post I will cover the way back from the Fish Tank.

Basically I drilled a 40 mm whole in the side of the tank (pic 3) where I wanted the over flow (after removing some of the water so it would not flow out). Then I drilled a hole in the back for leaf catcher (pic 4). Then I cut a piece of 90 mm pipe so that the water would be drawn from the bottom of the tank (pic 5) and then I attached it to the tank.

So basically as the water flows into the fish tank from the sump it will cause it to overflow out of the whole. However, we don't want to draw the water from the top of the tank. So we put a guard on there to stop that. To cause the water to come from the bottom we add the 90 mm pipe and put some slices in the bottom of it so the fish can not get up it but the dirt and water can.

More to follow shortly.

[aquaponics-shop]

Ok, I figured I would put up as much as I could for the moment as I might not get back to finishing this story. Anyway, picture 1 shows the completed overflow on the fish tank from the last post. This is before we put water back into the system.

This brings us to a major benefit of continuous flow systems. The water level is constant in everything except the sump. So when water is used in the system the sump level will lower. All you have to do is fill it back up to the top - no guess work in that. In our case we are putting a float valve into the sump that is attached to a 25,000 litre tank so it will keep itself topped up.

The second issue is that the fish tank can never run dry! Water is pumped into it and overflows back to the sump (picture 2). Hence it is not possible to pump it dry (as opposed to flood and drain systems where that is a real risk).

After the fish tank we need to get the water back from the grow beds.

The first thing we needed to do was remove the old egress pipes from the grow beds. One thing we had never noticed is that while the pipes running back were 40 mm (which is fine) the bottom of the egress pipes in the tanks themselves were only 20 mm. It does not matter what you do 20mm whole is not going to be good enough for a continuous flow return!

So I cut the 40 mm pipe at that was attached to the beds. Then I was able to turn them over and undo the old connection. It was a complex arrangement and in the past I have even had to use a hole saw to drill it out. This was replaced with a 40 mm tank fitting.

Picture 3 is showing the new tank fitting coming out of the bottom of the grow bed where the old fitting had been. I use Sikaflex to seal both sides of the tank fitting to ensure a good seal. While I am sure that the fittings will probably be fine without it I have always used it and not had a leak yet.

I tighten them down (picture 4) and then they make a nice 40 mm whole in the tank (pic 5). On the bottom I use a 40 mm iron to screw onto the tank fitting and then glue it into the existing 40 mm return pipes.

Still more to follow ...

[aquaponics-shop]

It is amazing how much '****' (can I say that here?) flows around in an Aquaponics system. In a flood and drain system it accumulates in the grow beds. After a while that will cause anaerobic conditions in your beds and all sort of things will go south from there. This is why they must be cleaned.

Picture 1 shows a bed with the gravel out. Remember these beds get cleaned out completely ever year and this bed had only been clean out 3 months ago!

In a continuous flow system we can do something about that. We use filters :-) Picture 2 shows the two filters. The first filter is for the water from the fish tank. The one the other side of the sump filters the water coming back from the grow beds.

These filters are super impressive!

Some people wonder why I filter water coming back from the grow beds. Well firstly there is a lot more stuff flowing out of it than most people might think. Secondly then you clean the beds (I will explain that in my next post) then a significant amount of rubbish (root matter etc) will flow out of the bed. The filter catches it.

Perhaps the most impressive demonstration of this is the final three pictures below. We used Canna clay balls in our systems. These release fine clay dust into the system when the water is first run through them. Note the colour of the water at the beginning of the filter coming in from the beds and the colour water coming out.

The system did get cloudy a little while after that because this shot was taken after I did the first bed. Four beds later the system was overwhelmed. This is not a problem really as the fish do not mind but we would like it clear.

Interesting it took 3 days for a two bed system to clear without a filter and less than one day for our 5 bed system to clear completely with a filter. I say 5 bed because we have converted one of the beds to duckweed and therefore no clay balls went into it.

[aquaponics-shop]

Continuous flow systems are very versatile. You can have media and medialess (loading raft) continuous flow systems. In fact you can mix and match as you like in the one system even.

In this case we used Canna clay media because we like it. It gives a gardenesk feel to the system.

It should be noted that you can not use gravel as the media in a continuous flow system. You need the fact that the clay balls will draw the water up to the roots of the plants - an effect that will not happen with gravel. Flood and drain can use gravel because they flood to get water and nutrient to the plant root and drain to get oxygen to them.

Anyway, the point about cleaning I said I would mention. Yes, you need to clean the beds periodically however it is infinity easier and better than with a gravel system.

Basically we put a stand pipe in the outlet as we fill the bed. This will cause the bed to 'flood'. In picture 1 you can see the bed just starting to flood on the left.

A few minutes later and the bed was 'full'. At this point the clay starts to float. This means that it also slightly separates. This is a major advantage when it comes to cleaning them (especially if you have a filter).

After we have a major plant growing period the beds will get a lot of root material and other solids in the beds. It is impossible to clean this out easily with gravel. We shoveled out the gravel and ran it through a cement mixer one bucket at a time to clean it with the old system.

With these systems all you do is put in a stand pipe to elevate the level of the water to the point that the bed is flooded. The clay will lift slightly and separate slightly. All you need to do is run your hand through it and stir it up. The smaller 'rubbish' will flow out to the filter and the bigger stuff (root matter mainly) will stick to your hands. So you just drag it out and put it on the garden - done.

I will finish this series off with a trick we apply to our systems. On the egress fitting (40 mm tank fitting) we put a male iron. But between the iron and the fitting we put a 90 mm end cap with a 42 mm hole in the middle of it.

We then put the stone guard into the 90 mm end cap. This helps hold it in place. We found that the system of just dropping the 90 mm stone guard in by itself is a real pain if you bump it and get media under it.

We also put a 90 mm end cap on the top to stop rubbish falling into the egress. Pictures 2 to 5.

We trust this has been of some interest.

Cheers

Martin and Kerri
Aquaponics Shop

[kenc45]

Hi Martin & Kerri,
Great post and great looking system. I think I'd find it hard to move from something that was working so well.
The filter looks great, and fairly simple, but how much is it, and how do you clean it? Does it provide good surface area for bacteria?
I like the idea of the end cap to hold up the stoneguard, and the idea of using the sump in the middle of the system as the common drain point.

What I would like more information on if you can is how the continuous flow in the grow beds works. Do you have to have lots of water outlets (or inlets I guess) near the bases of the plants, or just one? How deep should (or does) the water get in the bed? What are the benefits of this system?

I know that you mention benefits of continuous flow, but most of them have to do with continuous flow of the pump. You can have continuous pump flow (so no timers) and use the overflow method in the fish tank & still have a flood & drain (grow bed) system by using auto-syphons.

One downside that I have read (I am unpractised still) is that the auto-syphon can stir up the water - but if you are going into a filter, then into a sump tank, then that won't affect the fish tank at all.

Am I reading right that you aren't using auto-syphons, just continuously draining water through the beds?

Regards,
Ken

[aquaponics-shop]

Hi Ken,

Thank you for your feedback. We will do our best answer these questions as succinctly as possible.

I think I'd find it hard to move from something that was working so well.

It was working well but only with a lot of ongoing maintenance of the beds. Also every system we have converted from flood and drain to this model, both our own and our clients, has had a better yield and performance. The most outstanding example of that is the one we did for Linda (aquaponics@home). She had a two bed flood and drain system which we converted for her to a four bed continuous flow system and her yield differential was amazing. Suffice as to say she was very happy with the result.

The filter looks great, and fairly simple, but how much is it, and how do you clean it? Does it provide good surface area for bacteria?

Yes they are great. They are also simple which is also great as that makes them very reliable. They retail for $595 inc gst. There are several different sizes (weave pattern) of mat in them (see picture below). You simply pull the mats out when they are dirty and shake or wash the 'guk' onto your vegetable patch or compost heap. Yes they do provide a good surface area for bacteria (they are designed for that purpose). In fact they rely on that to increase their efficiency with particulate removal.

What I would like more information on if you can is how the continuous flow in the grow beds works. Do you have to have lots of water outlets (or inlets I guess) near the bases of the plants, or just one? How deep should (or does) the water get in the bed? What are the benefits of this system?

I have included a picture showing how the water ingresses the beds. It should be pointed out that we did sell 'distribution grids' with our systems but our new range does not include them anymore (soon to be updated on our website). When we first were introduced to Aquaponics we were told they were needed however since then we have done our own experiments. They are simply unnecessary. The only reason we put on a tee with this arrangement on the end of the ingress system is to minimize splashing (and it looked a little funky to us). In fact the pipe could just go straight down to below the clay balls and let the water flow in like that if you wanted. I hate distribution grids because they are unnecessary and require very regular cleaning (less with filters of course but you still will get significant bio-film build up in them). Water does not have to be delivered near the plants the clay balls take care of that. Picture 3 shows water running out of a bed. Basically the height is the same as the tank fitting with a male iron screwed into it. I have highlighted some of the benefits already do you mean specifically with running water at this level? If so there is no magic level it is simply the depth as described. You just have to make sure you have enough distance between the water layer and the plants (in terms of media) so they are happy (not a scientific explanation I know).

I know that you mention benefits of continuous flow, but most of them have to do with continuous flow of the pump. You can have continuous pump flow (so no timers) and use the overflow method in the fish tank & still have a flood & drain (grow bed) system by using auto-syphons.

Yes you can use auto-siphons and get the pump advantage. I am not a fan of auto-siphons though. They are great when they work but do require regular maintenance and checking. If they fail to draw then the bed remains flooded until you figure that out and if they fail to release the bed remains almost dry (particularly if you are using gravel and not clay balls). This is fine if you notice it quickly but if you don't it can be problematic. Also the water level keeps changing. It is much easier to look in your sump and just top it up to the 'full' marker than having to guess the approximate level needed based on the point in the flood or drain cycle; in my opinion.

One downside that I have read (I am unpractised still) is that the auto-syphon can stir up the water - but if you are going into a filter, then into a sump tank, then that won't affect the fish tank at all.

Yes, effluent from the beds is caught in the filters and that is a benefit of using one. I have not noticed auto-siphons stirring up the water any more than other flood and drain methods (once established) but if that was an effect then I would say it is a good one. People often talk about how good a filter the gravel beds are and how well they trap the solids v other systems. That, in my view, is not stating an advantage but rather a disadvantage. All those solids that they trap don't disappear - instead the clump together. Then you get some very bad effects. In short: clumping starts to cause an anaerobic condition in that area. This is bad as it causes denitrification and the production of some rather bad smells :-) The process has some systemic effects, like increasing the pH, and localized effects like killing the plant roots. The decaying plant roots then only increase the problem. Anyway, I digress ... the point is that if the auto-siphon arrangement you are wanting to use does stir up the beds and causes them to release solids then that is a bonus in my view (so long as it does not effect the plants). I have not noticed that effect in any of the auto-siphons I have used but I have not used a large number of different models.

Am I reading right that you aren't using auto-syphons, just continuously draining water through the beds?

Yes, no auto-siphons. They are unnecessary in this type of system because of the clay balls. They would be needed for a gravel system but as I have pointed out already I don't like gravel systems because of the maintenance issues. Basically the process of flood and drain in very simple terms is - flood for water and nutrients then drain for oxygen. In the model we use here we use a small constant level of water in the beds which can be accessed by bigger plants. The clay balls draw that water and the nutrients up to smaller plants. The plants are never immersed in water so oxygen is not an issue.

We hope this has helped you.


Cheers

Martin and Kerri

[GaryD]

Hi Martin & Kerri,

This is an excellent thread - full of good information for other members who may be experiencing similar maintenance issues with gravel beds.

We know that plenty of people have dramas with auto-syphons so continuous flow may be a good alternative for them.

As much as I liked auto-syphons, I've found life easier since I changed to continous flow several months ago. My first real 'up close' exposure to continuous flow was when we visited Kerri's place as part of the Commerical Aquaponics course back in January.

We had to tinker with water levels because I had too much water in the beds initially - but it seems to be working well now.

Our ongoing discussions have focussed on the need to capture and remove solids in aquaponics systems and I'm delighted to see that you've identified a simple (and easily maintained) filter device that may help to address the problem.

Gary

[Outbackozzie]

All of my growbeds have earthworms in them, and they have been going for well over a year now. A couple of weeks ago I dug right down into a bed, and there was no solids build up at all.

I agree with Gary regarding autosiphons - I have a mix of continuous flow and siphon beds, and there is absolutely no difference in growth.

[kenc45]

Hi Martin & Kerri,

Thanks for the very detailed reply. I appreciate it. This - though simple to some I'm sure, seems foreign to me as I have always thought that the flood and drain was needed. I'm always happy if the system can be made more simple.

So, assuming the beds are 30cm deep, how deep would the water in them sit? 10cm? 2cm? ??

I am trying to plan my system - still about a year before I can actually build it, so I'd like to learn all I can and have a great plan in place before then.

Thanks again.
Ken