Backyard Aquaponics
A place to discuss aquaponics

All systems are on a 3000L pump so the siphon and the CF are getting the same water turnover, probably about 2000L an hour turnover I would guess.

The action of the siphon would mean water coming into the growbed are sucked directly ou of the growbed. F&D would allow longer contact with the media. Thoughts on this theory?

I was leaning toward the same thinking Vlt... exposure of the media to the water....

Which would explain the performance of the constant flow bed in relation to all three...

Hard to tell if the siphoned grow bed exposure is shorter than that of the timer F&D system though... which is what I was really getting at with my question...

i.e ... roughly how many times does the siphon drain the bed each hour... how long does it take to flood before activating the siphon... and how long does it take to drain....

The timed F&D has contact with the water for the 15 min of flood... and probably 15-20 mins during the drain.... about 30-40 mins...

I wonder if the siphoned system is less than that... in total....

Interesting.

I raised this exact point in September last year - my theory relating to GB water detention/retention time. ie: the more time the water is exposed to the media and bacteria, the more efficient and productive the nitrification.

The thread was here.

I was pretty much shot down in flames ...

I am still confident that my theory would ring true ...

OK, Matt recoded the timing late today in the siphon system and I think it was about 7 minutes fill, with 2 minutes drain. Roughly... He might be able to fill you us in if I have it a bit out.

Might have to take some pics of our siphon as well, not at all conventional.. Our siphons run the drain pipe right down into the fish tank, submerged. Different, but they have been working well for us for at least a couple of weeks now...

When you fill your siphon the media has water contact. When the siphon starts, any water going in is sucked out quickly. This is especially bad if your siphon doesn't break to allow the water to fill again. Or, in the case of my system, the water going in will not allow the siphon to break due to the rate of the pump. I have not choice right now as my water needs the mechanical filtration.

it makes complete sence!!!!

I don't know if it makes complete sense... but it's a point worth examining by experimentation....

Members experiences have shown that there are some caveats.... like sufficient oxygenation, and sufficient filtration capacity to begin with....

Indeed, "C1" has run his systems as constant flood... with good results... but with large amounts of oxygenation and filtration capacity...

Having said that, when I last heard... he had converted back to flood & drain....

Both F&F & TCL have reported similar experiences... whereas in my experience I didn't see any gains what so ever in running constant flow... in fact my growth faltered... (hence my surprise)...

The trial suggests that for the systems as setup.... constant flow works almost as well as the timed F&D....

To me... the surprise was the under-performance of the siphon based system... and this might be a factor of water turnover... immersion time, or "detention" if you want to call it that....

Looking at the figures... the constant fill/drain of the siphon (as I'd have suspected)... seems to indicate a scenario very similar to a constant flow situation....

Yet the timed F&D system... where "retention/detention" would apparantly be the lowest... is the better performed...

Which is counter to the postulation that increased dention is beneficial... more time/work needed me thinks...

I would like to see what the performance of the flood and drain vs the constant flow system after 3 months or so when the root systems of the plants is more established/larger.

I thought one of the advantages of flood and drain was that it allowed oxygen around the root system.

Me too...

Some one got a time machine?

Can one of the modes please remove that above post of mine it gives no bennefet to the trials i put that in after to many drinkies as an answer to Arbe [ i would like to see what the difference when the plants become established]

Its still early days and I would not be suprised to see the siphon system come from behind to take the prize.
I think to accurately compare plant growth from the 3 systems, the water needs to come from the one fish tank?

FandD ftw always knew it was the way to go:)

Yea, I expect that things will change a fair bit over the coming months as the plants better establish themselves. They are in quite harsh positions out there as well getting full sun, and man have we had some sun over Christmas. The lettuce in all systems have shriveled up to nothing.

Having them all come from the one tank is an idea, but this is supposed to be getting results of the systems as whole individual units. Because they are separate units we have discovered that the nitrification in the timed system is slower than the other systems. If they were all hooked into the one tank we would never have known.

The basis behind these trials is to both help everyone make better systems, but also to help us provide better systems. From these early results I think we will be at least changing our initial cycling instructions of systems to say "leave the system running permanently for the first 4 weeks, then switch to the timed cycle". We might find that perhaps a mix of timing works better, 15/45 for a few hours, then perhaps run for an hour, then back to 15/45, changing it over a 24 hour period. I dunno, that's what this is all about, playing with things.