Backyard Aquaponics
A place to discuss aquaponics

Hi All

I am after a bit of advise from the experienced here, I believe in renewable energies and as such run a grid connected solar power system ( got the gov rebate as well) to offset my foot print somewhat and also run solar hot water, so I am trying to minimise the power used at my home. That brings me to the question, I have looked at Joels systems and I am going to start with a 4 bed and a 3000 litre tank, I will slowely construct it as when the funds are available so it wont be a turn key event, I want to minimise the power usage, I understand there are 2 ways people seem to run the systems 1- with low wattage garden fountain type pumps and they run them consistantly and the other way is with lets say a 300 watt pump at 15 min on and 45 minutes off type of cycling from the main tank, also the system uses a second pump to pump from the drain tank the the main tank. I thought I had it all worked out , sink the main tank into the ground and drain from the beds strainght into the main tank minimising tanks and pumps, but I had a niggling thought in the back of my mind that it cant be that simple. I watched the you tube install vdeo and there may lay the problem, aeration of the water, it seems the main tank aeration is run from the drain tank to main tank pump line via a venturi. Does the main tank need this venturi aeration and if not where does the oxygenation of the main tank come from other then the normal air, would a flow divider on the main tank pump line to the grow beds into a venturi and a fountain in the main tank be enough, I have run aeration pumps on other systems (sewer etc) and hate them with a vengence I know some people run them but I would like to avoid that and again that would be another pump. Any suggestions and advise would be great, I also noticed on one posting the person did the 15/45 cycle then turned his off at night completely.
Solar power - I have seen some posts on the topic in here at the feasibility, I have a 1.2 kw system that at present in spring is generating around 5 Kw a day, if I say run a 300watt pump on a 15/45 cycle all day the total power usage for that pump for the day would be approximately 1.8 kw, to offset this at this time of year with solar panels I would need 2.5 extra, lets say 3 panels which equates to around $4500.00, summer u would probably get away with 2 panels, winter - dont even do the numbers.
Now - who is shaking there head going "what dribble"? lol
7.00 am time to be out in the garden, until next time........

Bree

1 x 65 watt energy efficient submersible pump (4500lph) will run a quite large system on auto siphons. The amount of pumping per hour that is required is determined by your sticking density.

I have 2400 litres of growbeds that are above the tank and drainback into it. One pump running continuously keeps the water clean for 50 big trout.

I was also on the air pump hateing brigade, until I plugged in a 20 watt one, that runs beside a 65 watt water pump. A long air stone moves a lot more water than the water pump does. I think air pumps definately have their place in AP systems.

The water also gets aerated as it drains through the media in the GBs...I am also a user of a small continuously run pump and have had no DO problems to date (don't expect any either)...trout/barra require a higher level of DO and as such it is prudent to have extra air as OBO suggests...stocking densities can also dictate whether extra DO is required

With your tank partially sunk into the ground and 4 growbeds draining back to the tank...

You'll probably find that you have sufficient aeration.... both from that occuring through the growbed drain.... and from the water reteurn to the tank from the 4 growbeds....

I'd be tempted to run low wattage pumps continuously... but you could always run a single pump (like the Ebara) and set your timers to pump more frequently if required...

Your proposed setup is different than the standard kit that Joel sells... which returns back to a sump... which pumps to tank... which pumps to growbed....

In many ways, your proposed setup is the simplest and most efficient way of doing things...

As others have said ... you can always supplement aeration with airstones... I do anyway...

I too am very concerned with energy efficiency, Bree

Do a search on CHIFT PIST (Constant Level in Fish Tank, Pump In Sump Tank)
Here the fish tank is above ground and has the highest level (often 1 m),
That tank overflow drains with a SLO (Solids Lifting Overflow) to the growbeds which can be at working height (80 cm), and the growbeds drain into the sump which can be above ground too The sump (that holds the pump that pumps the water back to the fish tank) level would fluctuate say from 20 to 50 cm .
that means that head is fluctuating between 60 and 90 cm, depending on the size of the sump: a narrow smaller sump will fluctuate more than a bigger one with more surface
Unfortunately efficient pumps for these heads are very difficult to find (you will be lucky to find a pump that exceeds 15% efficiency) and I believe there is a lot of work to do there.
Most used are centrifugal pumps and these are all designed for higher heads.

One way to surely enhance efficiency is to pump only straight vertically upwards so as to keep the pipe length the shortest possible, then use a horizontal open gutter to lead the water back to the fish tank. The water, already aerated by the growbeds, will further aerate in the gutter and drop in the fish tank in a wide spray, to which you could add several small cascades in succession. I use share drain pipe 100 x 100 mm in which I dave drilled holes with a hole saw. It can be used as a NFT (Nutrient Film Technique) gutter to grow plants in.
As it is the highest element of my system (1.10 m), I have positioned it on the north side (I live in the northern hemisphere) so as not to shade the growbeds, especially in winter (light is very important too).
Making the water swerve in the gutter will enhance aeration even more.
Extra aeration with an air pump is only needed if you shut off the pump for longer periods. Make sure you never do that just after feeding the fish, as oxygen demands are then the highest.
Just go easy on the stocking density or pump more water around as relative fish density (kg/m³/hr) is more important than volume fish density (kg/m³) as far as water quality is concerned.
It is the factor determining density limits.

download my pump efficiency calculator here:
viewtopic.php?f=1&t=4150
make sure you download V4, as there were some bugs in previous versions

you can enter data from any pump chart there and compare pumps
or, if you enter several data from the same pump chart you can find out for what optimal head and volume it was designed



You pump seems to actually perform quite good, Outbackozzie: if the 4500 liters are delivered at a head of 1 m you reach 19.23 % efficiency.
But that is most probably not the case: pump manufacturers have the nasty habit of measuring pump volume at zero head and then use that figure to name their pumps.
If that is the case (please check), and the head at the volume of 4500 litres is only say 10 cm, the pump efficiency at that head is only a shocking 1.92 %.
You should input the data from the chart (and hope that these are sincere) or measure the head and the output to make sure.

You know I strongly question your statement that an airlift or an air diffuser moves more water for the same energy consumption than a pump.
I agree it gives the impression of doing so, but what you see is mostly the movement of the bubbles, not that of the water
You should measure that too and input the results in the calculator which will then return the efficiency
I am anxious to find out the truth in case I should be wrong
My last small air pump broke down, so I cannot do the test myself, and I don't intend to buy a new one as I don't believe in them.

Don't use venturi's on the outlet side of a pump as they greatly reduce pump efficiency: a venturi works only because there is a restriction in the outlet.
Rather use a tee on the suction side to allow the pump to suck a little air with the water as used in protein skimmers

hope this helped

frank

I think you should explain the Tee frank or someone might kill their pump before the water comes out and most use submersibles.

From talking to Bree the other night... he/she intends to use the slope of the land ....

Bury the tank... and just drain the growbeds directly back to the tank... hence, no sump... and a single pump....

Or at least I think I was talking to "Bree" the other night....

lots of aquarium pumps can be converted from interior to exterior and the fittings to do so (a suction tube) are delivered with the pump
drill a small hole in the suction tube and connect a peace of air tube to it so that it creates a slight disturbance in the inlet
put the pump back in the tank (there is no need to mount it outside)
take the other end of the air tube to above water level and put an aquarium valve on it to regulate the amount of air sucked in
... et voilà ...
the impeller will shatter that air into tiny bubbles. Special impellers or modified ones might improve that.
Put a stand pipe on the pump exit to just below water surface as inhaling the small bubbles might be harmful to the fish

Make sure you have a pump where you can replace the impeller as the bubbles could cause cavitation.

Frank

I'll take a photo of the appearance of extra movement of water with the air pump frank, it doesnt just look like a little bit more water movement, theres a ripple of water that moves a long way out from the air pump hoseing. Looks like a heap more movement.

a photo won't do, Ozzie, but thanks for offering
as I have previously admitted that the impression of more flow is undoubtedly present
so a photo can only add to the confusion

only measuring and the subsequent calculation can solve this riddle and prove me wrong
(in which case I will humbly apologize )

Frank

How do I measure the amount of water being moved by a 1 metre ring of bubbles?

in the case of an airlift pump you simply take the output of the pump from a tank filled to the rim over the side of the tank at the lowest possible level into a bucket and see how fast it fills
in the case of an airstone you imitate the airlift pump => you put a tube (of your choice, but accept the consequences) with an elbow or a tee over the air stone and bring that over the side at the lowest possible level
frank

I'll give that a go tomorrow, I am interested to see what happens I have some fitting that I am yet to use for my IBC's that should do the job just nicely.

Hi Ozzie,
I am very grateful that you are willing to go through the bother of doing the test
I feel I have got you intrigued somehow and that can only lead to a positive issue:
either I am wrong and I have to reconsider or I am somewhat right and my conclusions seem to be sound
I call both positive as I want to know more than I want to be confirmed

just a few suggestions:
you should put the air pump at full throttle for a first experience since that is when you know it is using the 20 watts and these are fully conducted to the airlift pump
but that might not be the configuration in which the airlift performs best as this might be dependent on lots of factors: air flow, diameter, submergence,...)
so a second and third try should be with reduced air supply to see if more water is pumped

anyway, I think you understand the possible complexity of such a test

I am perfectly ready to accept that, even should your first test confirm my idea, unless you say so, this cannot be considered conclusive and that more tests are needed
I would really like somebody to prove me wrong as that would solve a dilemma for me in the easy way...

That would almost have more value than the sad constatation that I might be right.

Because airlift pumps have so many possible and difficult to combine configurations that there always will be the possibility that one day one is proven to be very efficient..
so far I have not found any evidence
which doesn't exclude it

So I will probably always have to live with the notion that "might be" is an essential word in my conclusions

good luck with the test

Frank

Well, havent i started something here, Im understand about 1/2 of what im reading but learning really quickly, tell me why do I now lay awake at night thinking airstone, drains, autosiphons and the like, my partner looks at me with that "Your Obsessed" look - AGAIN. Aeration - I was thinking another way would be to take the return water from the GB's and run it through a flowform before going back into the fish tank, the same way that some biodynamic farmers aerate their water before use, also was thinking of the problem of when the growbeds are full and the FT is at minimum water level (and the fish hold their breath) (sorry my humur), John was saying to me that the drain tank is sort of used as a surge tank and a extra storage capacity, well if I got my min and max FT levels and selected the correct surge tank I could use an inverted "U" shape flooded linked pipe and the would maintain water level in the fishtank somewhat and then the grow beds wouldnt have such an impact on the FT and no second power consuming pump, now this is my theory, im sure there is a valid reason I cant do this, I think there is a lot that can be done with the return water to aerate it naturally, comments?

Bree