Backyard Aquaponics
A place to discuss aquaponics

Ok, Im am looking at building a small raceway and have some questions I wanted to throw out to fish for some ideas of what the best practice is for operating a race way.

-Method, Flood and fill from pond elevated grow bed, no sump
-Proposed water volume 5000 gallons / 18927 liter raceway.
-GrowBed volume 8000 gallons / 30283 liter
-Stock Density, ~ 1000 fish
-Solids settling area before pump to growbed to optionallt remove solids.
-Air via returning water and air pump or paddle wheel
-Water pump, Electric start diesel water pump, electric pump, or other method
-Water Volume in Race when grow bed is flooded 2668 gallons /10099 liters
(Based on Small brown river pea gravel displacing 66% of water)

I want this system to be as efficient as possible so here are the questions I am "thinking on" and would like input on.

1) should I pump water around the raceway, or pump from one end and return grow bed water to other end?
2) Should I use a paddle wheel?
3) Should I use Air stones?
4) What pump is best suited for 2 to 3 foot lift? Perhaps a water bucket wheel that lifts the water up to a tray that brings the water down to the grow bed?

I am thinking a lifting water wheel to lift water, and a paddle to keep flow in raceway all powered from a single motor.

Input? Suggestions? Experience? Opinions?

I climbed over the fence near the Cotter dam in Canberra to sneak a peek at the old trout farm. The raceway has a lot of corrugations in it and also has a waterfall-type drop into each tank.
If it's enough oxygenation for trout....

Sorry, no pictures.

1. pump from one end and return grow bed water to other end.

2. Dont think it would be required.

3. As above, your stocking density will be extremely low, however they should be used as a back up in case of pump failure.

4. Your talking about a heck of a lot of flow, I dont think a bucket wheel will cut it.

This is a very large idea, and is going to need a decent sized pump to circulate the water to such large growbeds. Ideally you will want to turn at least 5000 litres of water over per hour for that amount of fish, this can be done with around a 100 watt pump. Personally I'd get the biggest pump I could afford to run.

A diesel pump does not even enter the equation.

If you haven't already seen this: In-pond raceway, it might give you some ideas. Not exactly what you want, but food for thought...

I'm sure there will be someone who doesn't like the idea...

I was going to put in a waterwheel, but decided that it would probably lead to a fairly high water evaporation rate so have shelved that idea for now.

dividing your growbed in sections and filling/draining them in sequence would allow for much less level variation in the fish tank

with a cross section of 1 m² your fish tank will be 19 meters long and you will have 40 m² of exterior tank surface
you will then also need a 19 m long pipe or gutter to bring the water to the other end
you could make a U-type raceway (with a divider in the middle) with a cross section of 2 m² which allows you to halve that length and reduce the outer surface to 23 m² and reduce all piping lengths to say 1 meter
A W-type raceway (three dividers) with a cross section of 4 m² would further reduce outside surface to 17.5 m².
alo the footprint will be much less should you think of a greenhouse over it
Outside tank surface is expensive as it must resist water pressure
dividers are under no pressure at all and can be cheap
less outside surface means less temperature losses, more temperature stability
but you speak of an in-ground tank, I believe?

the bigger your (centrifugal) pump, the better chance you stand of finding an energy efficient one
the pump OBO suggests (5000 litres @ 1 m head) has an energy efficiency of 14%, which is to be considered as reasonably good as far as small centrifugal pumps go.

a water bucket wheel if well designed will be MUCH more efficient as it is a positive displacement pump
with the right motor, energy efficiency of 80 to 90 % can be reached

I have a very low opinion on air stones and airlift pumps, but will not repeat it here as this raises the hairs of some members and I have no mood for another discussion on the subject. Just do a search on "diffusers frank" to view it.

maybe make a sketchup drawing of your proposed setup?

most interesting link, Mylesau, thanks for it
I like the idea VERY much

frank

Frank designed a rather interesting passive oxygenator, its in the sketchup components (not sure if he's tested it yet). If you pumped from one end of the raceway to the GBS and returned to the other end via the oxygenator you would only require one pump (to the GB's). To make it efficient you would probably have to have the GBs along one side of the raceway (or both if your going bigger ) and do a 90 degree passive oxygenator for the return (not a biggie more DO).
Biggest problem I could see is getting the drop (for the F&D) then having sufficient drop for the oxygenator.

Actually that "Pond in Raceway" link would seem quite simple to implement... and has oxygenation and solids settling built into the design....

Uses a series of airlifts for oxygenation and flow dispersal... quite "effective" ... even if not "efficient" ....

Still got the problem of the lift required by Dan, that was 2-3 feet.

Thought that was all Dan needed ... 2-3 feet...

Rupe

Unless I read that wrong they are using the airlifts to move and oxygenate the water not to lift it.

Way I read it Sleepe ... it does all those things.... but in fact it it "the pump" as well...

No other pumping mechanism indicated in the text or drawings ....

Page 2
"One of the most common IPRs has been built of treated plywood, framed with treated 2x4 lumber or
steel, and coated with epoxy paint. Sizes have been either 16 or
24 feet long, 4 feet wide, by 4 feet deep (only 3 feet underwater)."
While they state they float, I think they mean they just float.

Has anybody thought if useing ap water you would have to keep it covered otherwise it woud go green slimey

the passive oxygenator in the drawing is only 100 x 100 mm in cross section (so only needs a drop of 10 cm) but it can be made to whatever size
I will test it later this week for functioning, but will not be able to prove anything with hard data as I don't have a DO meter
I will take a picture of the water flow before and after, maybe that will show a difference

the in-pond raceways don't float on the water, they float in the water
there is no head to cope with

that brings up maybe a "novel" idea for moving around the water in the raceway:
how about a "trolling" outboard motor used to power fishing ?
12 V battery powered
http://www.minnkotamotors.com/products/ ... .asp?lp=gb
installing it in front of a pipe might even give you the necessary head
then it would become a propeller pump which are considered as very efficient

or installing a smaller pipe in front of it might lead part of the water to the growbeds

frank

Stick a simple flute on the ends of the venturi and you may have invented a 'wind chime for' AP.

BTW "the in-pond raceways don't float on the water, they float in the water"?