Jonty's new system

[Jonty]

I originally set up half a blue (220 litre) tub on the goldfish pond as a trial. This pond was always green and the fish lethargic. Today the water is crystal clear and the fish are very active. The only problem I had with the system was getting the auto-syphon working correctly. When I mastered this feat I decided it was time to go a little larger before I branched out further.

I had a 900 litre black poly tank so I purchased a 585 litre grow bed from Murray. I had two objectives in mind. 1. It had to work on the KISS principle (Keep It Simple Stupid). 2. It had to be energy efficient.

The grow bed was placed on a hardwood bed 800 mm off the ground. The total height is 1.1 metre. (Incidentally it is a good height to lean on). I needed the bed at this height so the auto-syphon would deliver the water straight back into the tank. This required the tank to be dug into the ground approx. 200 mm.

I then ordered the stones. These were then put into the grow bed unwashed. I then cycled the system for a day. The water in the tank was brown and thick. I let it settle overnight, then raised the pump into the clearer water and filled the grow bed. The remaining water was used on the garden. The water cleared after 2 days and I can see the bottom of the tank. I added some gunk from my goldfish pond as well as some Seasol to help the system along.

The system consists of a 1,500 litre pond pump rated at 20 watts. (Pump runs continuously). The pump delivers the water to the grow bed through 20 mm electrical U-PVC pipe. I have set up a 90 mm stormwater pipe below where the water enters. This pipe goes to the base of the grow bed and has slots routered into it to allow the water to disperse. (I have found it better to allow the water to rise in the system as any debris is kept at the bottom and broken down quickly by the bacteria).

I have used 20 mm U-PVC water pipe as the up stand. The end has crenulations to enable the end cap on the auto-syphon pipe to sit squarely. The auto-syphon pipe is made from 90 mm stormwater pipe with an end cap. The top of the end cap was drilled and a rigid PVC pipe inserted the same length as the pipe. On the outside of the end cap I attached a T- piece (green aquarium type), then attached two pieces of silicon tubing that go over the sides and are held in place by tie straps. These tubes are open to the atmosphere when the grow bed is empty but are covered with water as the bed fills. This ensures that a vacuum is created in the auto-syphon when the bed fills so the syphon will kick in. When the water reaches the end of the rigid PVC air is drawn in and the syphon stops.

The auto-syphon works like a dream. The cycle times are as follows: From when the grow bed has emptied until full takes 27 minutes. The auto-syphon empties the grow bed in 14 minutes. Total cycle time is 41 minutes.

At the moment I have 3 silver perch in the tank. All I need now is time for the system to sync. I intend to use a computer UPS (Powerware 3105 UPS 700VA/420watt - $105.00) connected to a 240 volt 2 watt aerator as an emergency backup as I do not have to worry about water flooding from the system.

[Murray]

Looks fantastic Jonty. I am particularly interested in the way you have used the auto-syphon. The cycle time is excellent.
Good use of a small pump. I think that is an excellent model foe a small system. Do you have some pix of the auto-syphon setup before you installed it that you could post ?
Murray

[GaryD]

Hi Jonty,

Congratulations on a very tidy little unit.

I commend you on the fact that you have covered your fish tank. One of my enduring anxieties about Aquaponics is the possibility of children or pets being able to get into fish tanks.

The size of your pump means that you'll be able to operate your system without mortgaging your house to pay the power bill.

Excellent work!

Gary

[Macca]

Hi Jonty, can you explain the purpose of the air hose. I'm not sure I understand.

[Jonty]

Macca,
Have enclosed a breakdown of the syphon. Will post some photos Friday so you can see it in the flesh.

In the drawing the first pipe shown is the 22 mm with the crenulations (looks like a fort). The next piece is the 90mm stormwater pipe. Next to it is the end cap.

The end cap is drilled and a tube is inserted that is the full length of the 90mm pipe. The green T piece is inserted in the top of the end cap. The inserted tube and T piece are glued or silasticed into the end cap so no air can escape, however the tube and the t piece must have no restrictions when you blow through the tube.

I then silastic the end cap on the 90 mm pipe and attach two pieces of air tube and fold them over the side of the pipe and secure with zip ties. The tubes need to be underwater when the grow bed fills.

Here's what happens. The grow bed fills. As it does a vacuum is created in the 90mm pipe because the long tube in the pipe is covered with water along with the outside tubes. Any air in the 90 mm pipe is compressed until it is forced out through the 22 mm pipe. The syphon then kicks in.

As the water is syphoned out of the grow bed, it gets to the stage where the water level drops below the inside tube. As this tube is vented to the atmosphere through the green t piece, air is sucked in and the syphon ceases to function.

Hope this helps

[Macca]

Okay - so the bit of pipe connected to the green t runs inside the 90mm but outside the 22mm. Think I get it. Thanks.

[Murray]

Excellent Jonty, looking forward to the pix. I really have to give this auto-syphon thing a go.
Muzza

[Frank]

Excellent Jonty, looking forward to the pix. I really have to give this auto-syphon thing a go.
Muzza

So how do you drain your tank then Murray?

[Murray]

Gravity, out of the bottom of the grow bed into pipes that lead back to a sump which gets pumped back to the fish tank.
Muzza

[Frank]

So, do you mean that it just runs in the top and out the bottom continously?

I thought you had to let things dry out for a while. Don't you get root rot?

[Jonty]

Hi,

Have taken the photos of my auto-syphon.

The first one is the crenulated drain pipe (blue washer at the bottom is to ensure a water tight seal). The second show the air tubes coming out of the end cap and T piece. The third show the pipe inside the 90 mm pipe which is attached to the end cap.

When the cap is attached over the 22 mm drain pipe, the long pipe needs to go inside the 22 mm pipe to work properly.

Also have attached a photo of my original blue grow bed.

Regards
Jonty

[Murray]

Frank,
The cycle takes about 45 minutes to complete. It is commonly called "Flood and Drain" which is what happens. The pump in the fish tank pumps the grow beds full (almost), then switches off and then the grow beds gradually drain back to a sump. Water is moved out of the sump back to the fish tank, and so the cycle is completed and repeated.

Murray

[Frank]

Fair enough, so I presume you use a timer and switch the pump back on after the drain cyle and the drying out time. Correct?

[Murray]

Frank,
You could use either, both can work just as well. It gets down to a matter of personal preference. I use float switches. I find them reliable, although a little fiddley to adjust in the beginning.
The trouble with timers is to source a good timer that is accurate. I have tried a few and found that I could only find one that timed down to 15 minute increments.
My 15000 lph pump that brings the water to the grow beds from the fish tank only takes 3 to 4 minutes to do that, so it would be a waste to run the pump for 15 minutes. The pump output would need to be restricted back so as not to badly flood the beds if running for 15 minutes.
The other problem I have found with timers is that on one cycle it may switch for 15 minutes, the next time it might be 12 minutes or 18 minutes.
Too unreliable.
If anyone can point me to a good timer I would be very happy.

Muzza

[GaryD]

Hi,

By way of an alternative, I use an electric timer on my small (one square metre) gravel/expanded clay grow bed.

I use a tiny aquarium pump to lift water out of my fish tank into the grow bed.

I have a valve on the drain line with which I adjust the rate of flow from the drain back into the fish tank.

I agree with Murray about the lack of consistency when it comes to electric timers, however, a combination of restricting the drain and matching the size of the pump to the grow bed enables me to get it working OK.

Gary

[almiper]

I may seem a little slow here, but i still don't understand the auto syphon set up and how it works. could anyone enlighten me?

Thanks a lot

Alex

[daniel]

Hi all.

I was a bit confused by how the self-syphon worked too. I still am unsure how Jonty's system drains below the level of the small silicon tubes on the side of the 90mm pipe. That doesnt seem low enough to drain enough. I probably just dont get it.

I have drawn some diagrams below how i would have done it. I dont know if it would work...... anyone got any feedback?


Thanks in advance..

Daniel

[Jonty]

Daniel,

In my system it doesn't matter what length the outside tubes are as long as they are covered when the grow bed fills. If you look at your last diagram for the syphon you show the outside tubes reaching to the bottom of the syphon and you have a small pipe inside.

My is the same as your diagram except my inner tube is the length of the syphon and the outer tubes are smaller. As I said they only need to be covered as the grow bed fills. Same principle - varied design.

I made my inner tube longer as it is easier to insert into the drain tube. I wanted the outside tubes smaller as there is less chance of any debris blocking them. I just experimented until I got a syphon that suited my particular needs.

Regards
Jonty

[daniel]

Ok,

In that case, I guess the siphoning action must overpower any air coming in from the small outer tubes as they are so small.

So in your set-up, the siphoning must stop when the water reaches the lowest point on the 90mm pipe?

[Jonty]

Daniel,

I know how hard it is to get a handle on these syphons. Took me a few months to perfect from different designs. My hair is greyer and there is less of it.

No air can enter my syphon from the outside whilst the grow bed is filling. The green T piece connects to the inner pipe. Both of these are sealed into the end cap (airtight). For air to enter it needs to be drawn from the outside tubes down to the bottom of the inner tube.

As the grow bed fills, any air in the syphon is compressed until such time as the weight of the water forces it out through the drain pipe. The height the water fills in the grow bed is determined by the height of the drain pipe. The syphon starts off as a dribble but when all the air is exhausted, the syphon kicks in.

I can see this as I have a clear piece of pipe connected between the drain pipe and the outlet into the tank. When it starts to dribble I can see lots of air bubbles but when it kicks in the water is solid - no air bubbles present.

As the water level drops, it gets to the stage where it reaches the bottom of the inner tube, air is sucked in and the syphon immediately stops. The cycle then repeats.

Regards
Jonty

[Macca]

Jonty, do you have any idea of what the in flow into your grow bed is?

[njh]

(I have found it better to allow the water to rise in the system as any debris is kept at the bottom and broken down quickly by the bacteria).


Has anyone else found this to be true too? I had been carefully thinking about adding my water to the top (despite the added complexity), but if adding to the base is equally or more effective; that saves me a lot of mucking around.

[Jonty]

Macca,

I am using a pond pump rated at 1500 lph at a 180 cm head with a 585 litre growbed. I haven't work out the inflow rate, so I will do a displacement test for the grow bed tomorrow then work out the flow rate. Will post it as soon as I know the results.

I haven't worried about cycle rates or tried to reduce the pump inflow because I reckon it doesn't really matter. With my blue grow bed, I conducted a series of tests to see how plants coped with various cycle times. I concluded that cycle times were really immaterial.

On one test I had the water filling to the top of the grow bed, then draining out through the drain tube - minus the syphon (grow bed was continuous flow). Ran this test for 3 weeks. I removed some of the stones so half of the grow bed was at a lower level. I found as long as the growing centre of the plant was above the high water mark, the plant was okay and continued to grow. If I got water onto the growing point, the plant quickly turned to mush.

In the new system, the height of the water is controlled by the drain tube. The water fills to within 15 mm to the top of the stones, this way the growing point of the plants never get wet and evaporation is minimised.

I am still on a big learning curve with all this, but I do experiment a bit to see how things come together and what the results are. All I know is I am happy with what works for me.

Regards
Jonty

[GaryD]

njh,



Has anyone else found this to be true too? I had been carefully thinking about adding my water to the top (despite the added complexity), but if adding to the base is equally or more effective; that saves me a lot of mucking around.


I can see no reason why it would make any difference whatsoever.

Gary

[Jonty]

Macca,

As per Murrays specs on growbed - 2120 x 920 x 300 internal. Worked out the volume at 285 height (water comes to within 15 ml of the top. Total capacity 555.8 litres.

Used a 2 litre jug. Filled to 1 litre and added stones until they reached the 1 litre mark. 450 mls were displaced. Displaced litres were 250.1 amking the volume of the grow bed 305.6 litres.

Growbed takes 27 minutes to fill. This equates to 11.33 lpm or 680 lph.

Regards
Jonty.