Backyard Aquaponics
A place to discuss aquaponics

Did you also meter the amount oh kWh used by each system? Would be interesting...

With the growth difference perceived looking at the recent pictures, do you still recommend constant flow over the others? How's the water quality/clarity/DO?

Hi Earthbound

Can I just say, I think it's fantastic that you have set up and run this experiment.
I know it has made me rethink my whole system. I have a few questions.

Is the fish tank 1000 litres?
is the growbed 500 litres?
is the pump 3000 lph.?

Have you measured the actual flow into the growbeds.

Reason I ask is:

In the timed flood/drain bed, the pump will probably deliver 2400 litres/hour at that height
and if on for 15 min only will pump 600 litres/hour hence not cycling the full
fishtank volume hourly.

I am basically questioning whether there is any truth that the FT volume needs to be turned over hourly.

And if not, how often should it be ?

cheers Lou

Hey Lou,

Yes, yes, and yes...

Ummm, and so far as the idea of turning over the fish tank every hour, well, it's a good rule of thumb, but I hate to use that term, for people designing their own systems.. My big system at home only turns over about 1/3 of it's volume every hour yet I have raised some good crops of fish in it..

Haven't measured the kW yet, did buy 2 arlec metres that are supposed to do it but neither of them have worked. We will measure their power consumption one day soon when we can get things working. Luckily this is something that isn't going to change over time.

Water clarity is good in all systems, we haven't measured DO levels though, maybe when it warms up a bit...

With the CF, I gather you can get a far lower output pump and therefore this would be the cheaper option - electricity wise?

It would be interesting to run two constant flood systems side by side, but with different flow rates, to see if there is any impact.

Probably.. Ours are the same pumps in every system. The problem when you decrease the size of the pump is that you loose solids moving capability. There's no build up in any of the systems on the floor of the tanks, we'll see how they go as the fish get bigger. But the smaller the pump the less likely you are to move any solids..

Only about 3 more months and these trial systems will be a year old..

A trial of different size pumps or flows with CF would be interesting. I do know you need a certain amount of flow to keep the dissolved oxygen level up enough in CF to make it work. And the solids handling capacity of the pump is pretty important too.

Trial System Data & Progress Photos 19-09-2011

Trial System Data & Progress Photos 26-09-2011

Trial System Data & Progress Photos 03-10-2011

I am convinced constant flood is the way to go for my systems, 90% of the disasters i have had were due to siphon failure.
I would love to see the data put into graphs so i can see visually what the systems are doing.

Use Affnan's siphons

May i suggest Kill-A-Watt watt meters. Cheap $26ea and reliable.

Or perhaps Not so reliable... At least not the ones I bought.. Bought two of them, neither work.

well.. i eat my words

I've got two of them, the first was killed by a amp over load. (Parents plugged their hot tub in to see what it pulled, it pulled the life right out of it)

The other i've had hooked up to my workstation for over a year. If they were new contact the manufacturer i've heard great things about their customer support.