Backyard Aquaponics
A place to discuss aquaponics

Hi guys
how can i calculate the right pump size for my system?
I know I need to take into account the height above the pump that it has to send the water to, and probably the number of fish i wish to stock?
Ive only ever dealt with little pumps and small 50 litre systems.
i thought perhaps there might be a standard caluclation.
Can we use my system as an example?
Its approx 2225 litre pond
4 grow beds 250 litres each
grow beds are approx 1.5 - 2m above the floor of the pond
water drains from grow beds straight into pond.
thanks for your advice!

Aeon

Hey Aeon,

I think with your growbeds draining straight back into the pond, you will have good DO. I think it's all about getting enough turn over through the beds and out of the tank, ie, how many times per hour are you going to be putting fresh water back into the tank.
Are you running the pump continuously? Or do you want to pump fast into the beds so they flood and then have the pump switch off via a float for the drain cycle? What sort of grid do you have on top of the beds for dispersing the water? If you have a lot of holes etc and a complex grid, you will need a gutsier pump to get water evenly to all the holes, ie otherwise the ones at the end may be a bit slow. Also, if it is a bit slow, they will tend to clog up more.
Definately check out the head rating chart on the box of whatever pump you choose. Head is rated at how high from the top of the water to the top of the growbeds.(sorry if you already knew this)

I have Murrays' salt water pumps, 140l per minute, 3700 litres of water, 2400 litres of growbeds less than 1 m head, and I would say that was about as small as I would want to go just doing a couple of test pumps.

So, I probably haven't helped at all, but there's food for thought anyway.

Hey Monya
Thanks for all your info!
I'm not sure which of Murray's pumps you mean but I am hoping his submersible pump for $143 is powerful enough. (I think its 240V?)
I am most likely going to have a continuous flow system and a pretty basic irrigation grid- I'm hoping Murray can help me out with irrigation pipes as well as I'm too bloody tired and pregnant to go to Bunnings again in the next few weeks and the thought of having everything sent to me via post is very inviting.
It funny i was so elated to have the basic infrastructure built after waiting for what seems like years and now the next day I am am so tired and flat I cant even bring myself to go outside. I hate having to wait again till someone with muscles and a rational mind can come and help me out. Thats a whole week and my poor system is just sitting out there lonely and empty with no one to tinker with it. Torture!!!!!
At least I can do research on the forum!
Cheers
Aeon.

this is an interesting question, as soon as it looks like a standard is being reached someone comes along and blows it all away, michael ferrini is a prime example:
his fish tank size 500 gallons - about your size
pump size 100-120 gph (approx 500lph.)


My tank is 200 litres, grow beds 160 litres combined, pump 900 litres @ 1 metre and that is probably a big over-kill

about as much help as Monya I'm afraid

Aeon, my pumps are the $258.50 ones

The cheaper ones are pretty gutsy!

aeon i have murrays pump in a 300L tank and it pushes a lot of water 18 sec for my flood and i restricting the flow....

Check out this link to calculate your pond pump size: http://www.creativepumps.com.au/Pumps/q ... /chart.htm

nice one derek

Aeon, as monya stated it will be a function of tank voulme turn over per hour that you want.

I have heard figures of two volumes per hour and 3 volumes per hour.

What i'd like to contribute is that i don't think its as simple as stating a tank volume turnaround per hour unless you are going to stock at 100% capacity.

I mean i wouldn't think that a 1000L tank with 5 goldfish and a 1000L with 20 1KG perch would both require 2000LPH turn over. Know what i mean?

I'd be happy for others to comment on my theory.

Unfortunatly that means that i cant give you a simple answer.

I just didn't want you to go and buy a 6000LPH pump if you didn't have to.

BUT if you WANT an answer that will cover you to 100% stocking then...........2250x2=4500LPH

6600LPH @ zero head pump X 70% efficiency at 2m head = 4550 LPH turn over

Go for a 6600LPH pump.

Make sense?

The 70% @ 2m is for my pump, each will vary depending on max head capability of the pump, but it should be asfe guide if you're using the same style and type of pump as stu.


Steve

Yup
That makes sense Steve.
Murrays submersible 240V pump does 12000 LPH so hopefully it will be a suitable choice as I like the price on that one.
Aeon

Aeon

What is your bed size?
Any floating culture planned?
Tank size at volume you fill it to (not total volume)
What system? ie: continuous flow, ebb and flow DWC etc
Greenhouse or no?
What is the highest point in your system?
What is your medium size?
How much direct light gets on your pond/tank?
Gravity or secondary pump for retuning water?
Venturi or gravity return for air?
Porous or solid medium?

Hi Aeon, I have just answered your PM,
I have two of the 140.00 Stainless (China) pumps on test in my 600 ltr system and they work very well although the one returning the water form the sump is a bit overkill for the job it is doing. It could be 1/4 of the capacity and still do fine. The one pumping from the fish tank to the grow bed is also a bit over the top for capacity, but will not be when I hook up a few more grow beds over the next few weeks. I am finding the need for a bit of capacity in the pump out from the fish tank to make sure the solids (fish poo) etc make it through the distribution grid atop the grow bed, especially at the extreme end of the grid. So a bit of over capacity is not a bad thing.

I am about to run a couple of those Italian pumps in my system, I want to compare them to the el-cheepos just to see the difference.
I have one of the test pumps(only one months work) to anyone who is starting out for 70.00 (half price) plus 15.00 post (I am holding one for a forum member) if anyone wants one to start with.
Muzza www.aquaponics.net.au murray@aquaponics.net.au

Hi Aquadict,
Murray has offered to design me some irrigation so I have to find out the answers to all those questions for him too! thanks Murray)
I will do some measuring today and get back to you. I think i will take Murray up on his offer for a half price pump and any feedback from you as well the re the info I send is really appreciated!

Hi Aquaddict
Here are the answers to all those great questions you asked:

SQUARE GROW BEDS x 4
900 mm W x 900 mm L x 300 mm H
volume: 243 Litres each
Length of entire grow bed rack: 4 M and 5cm from one end to the other
There is a gap between each grow bed.
Each grow bed has a space of 12 cm between it and the next one
This gap widens at the corners of the beds as they are not perfectly
square - the corners are slightly curved. At the far corners the space
between each grow bed is 25 CM wide

EXTERNAL POND SIZE:
150cm W x 300 cm L x 65cm D

USABLE POND VOLUME
I approximated the filled tank volume:
250 cm L x 140 cm W x 60 cm D= 2100 Litres

SYSTEM COVER
In the summer the system will sit under a plastic canopy a bit like
Joel's and in the winter I'll add plastic clear vinyl walls so it will
be like a greenshouse when its cold.

HIGHEST POINT
The distance from the floor of the pond to the top of the grow beds is 140 cm
140 cm is the highest point in the system

SUNLIGHT
two thirds of the pond surface gets direct sunlight in summer for
about 5 hours of the day however I will place a timber lattice frame
on a diagonal angle over the top leaning on the lip of the grow beds
down to the edge of the pond and grow some vines over it to reduce the
light and remove this in winter when the sun disappears from my garden

PUMP
One pump only from pond to grow beds then water gravity feed back to
pond with beds directly over pond

AERATION
Initially just gravity air return via drain pipes splashing water from
grow beds drectly into pond. i will assess the dissolved oxygen levels
and include a venturi or aquarium bubbler later if neccesary

GROW BED MEDIUM
approx 1 tonne of 6-10 ml red scoria - very porus

Thanks so much for your interest - it was a really good opportunity to assess my system.
Hope I didnt miss anything out
Cheers
Aeon

OK. Very good details thank you. murrays pump sounds a good deal I don't know the flow rate though. I'm going to ramble here, a fair bit of it's tied in to the rest just a bit disjointed on the bevvies...

One question. Ebb and flow or continuous flow beds?

The scoria rock takes approximately 50% of space, or displaces approximately 50% of water (mine was said to be 25mm but ranges from 5-50 with most being 25ish). Your current bed volumes are 1000 litres approx. This means they'll hold approx 500 litres water.

For ebb and flow you could run from 500 litres per hour at your plumbings highest point (1 turnover of water) to 2000 litres per hour (4 x turnover) in those beds comfortably, and quite possibly more.

The lower range of 500 lph is not enough turnover for your pond really, nor air. If you move the water at 2000 lph or more, your pond is turned over once an hour, or 24 times a day. According to your stocking rates, this should be enough movement and air.

For continuous flow I recommend the 2000 lph plus range because of the above paragraph.

Each kilo of fish (polyculture, ie omnivores and carnivores) takes an approximate 1/2 m2 of bed at your depth to filter it. From your beds area I determine as your beds begin to flourish you can safely stock up to 20 kiols of fish. More fish will require either more beds or water changes of percentages appropriate to excess fish population. In other words, when you get about 20 kilos, start eating em, or making more beds.

Starting at a flow rate of 2000 lph, your bed capacity in ebb and flow could easily be doubled without need for another pump. More pump than you need is fine, to an extent, you can redirect it for aeration or in pond circulation.