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If you are growing using Flood and Drain on a timer, how often to you cycle and for how long?  I think most of us use 15 minute interval timers, so I'm guessing that the duration of a cycle is typically 15 minutes - I know mine is.  I tend to go 30 minutes between cycles if everything is nicely balanced and only 15 minutes between if I'm overstocked with fish and need the oxygen more than the plants need the dry period - which is where I am in 2 out of 3 of my systems now.  The other data point I have is Joel at Backyard says he typically goes 15 on / 45 off with his systems. 

What do you do?  What have you found works best, and what just doesn't work?

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thanks for pointing that out, Christopher!  Very interesting, and I"m also surprised at the results.  Thought the siphon would kill it (and our systems currently run off timers!). Not accusing anyone of anything, but it is worth considering that that Joel's Backyard systems are all run using a 15 on 45 off timer cycle, and his main competitor, Murray Hallam, uses bell siphons in all of his. Joel is a smart business person and I can't imagine that he would let his horse lose this race - especially not in a public forum.  Maybe Murray should run a similar test and see what happens... or best of all, someone without a horse in the race should run the race.

I"m going to post the video they did in our videos section.  Wading through some of the 14 pages of chatter is time consuming but you can get the general idea with the video.

Hi, It is interesting to follow the tests being done on BYAP. 
We did the same tests about 3 years ago and ran them for just over 6 months.
We have built and delivered systems as big as 20 grow bed system (150 gallon beds) and running auto siphons..... works just great.   We have also built and commissioned a 20 grow bed system (150 gallon beds) using a timer, sequencing valves and large capacity pump.....also works really well. 
I can expand on how these two systems compare if anyone is interested.

We found no observable difference between timed flood and drain and auto siphon flood and drain as far as plant growth or fish happiness and health is concerned.
We did not enjoy good results with what is termed "continuous flow"
As a result of those tests we decided to run with auto siphons over timed pump outs because of several advantages

1 Smaller pump/s can be used in any given system (working towards solar driven systems)
2 Pumps last longer when being run continuously.
3 Do away with a possible fail point, the timer.
4 Using auto siphons, in a multi grow bed system, they fire randomly so the fish tank or sump is not pumped down too far.
5 Larger systems that dump water back into a sump, can deliver water continuously back to the fish tank.

In summary, the most important advantages are that the pump can be smaller, last longer and a possible fail point has been eliminated.  In smaller multi bed systems the random nature of the water dumping mean that the fish tank or sump does not need to pump down so far.
Having said all that, you will enjoy good success if you decide to build using a timer and flood and drain provided you make sure you get a good quality timer.
 Happy Aquaponics

Murray

I should have known you would already be ahead of the game, Murray!  Thanks for jumping in.

Guess what.  It all works

 

Some things work slightly better in specific circumstances but it generally seems that there are always exceptions.

 

I believe an important point in the Constant Flood is that it needs to be constant flow at a high enough rate to keep the oxygen levels good.  If the bed is constant flood but intermittent flow or very slow flow, things may suffer.  And anything with constant inflow is likely to have more issues with media sliming where the water enters the grow bed.

 

Timed flow into the grow beds doesn't seem to have the issue with sliming at the inlet.  I've never done the inlet distrobution grid as BYAP does but it might be a good idea for constant inflow like on siphon or constant flood beds.

 

I've got quite a lot of beds getting timed flood and drain in a few methods of operation (either the pump is turning on and off feeding an indexing valve or I've set up some other means to operate an indexing valve) Most of those beds get flow for about 9 minutes out of each hour (that way a bank of six beds can each get flooded once an hour.)  So timed flood and drain that way seems to work quite well for the plants at least.

 

I also have some constant inflow flood and drain beds, one by autosiphon and the other by float controlled pump.  They seem to be doing ok but are not as impressive as I would expect.

 

My constant flood/flow beds actually seem to be doing better than my autosiphon beds.  Go figure.

 

Hi TCLynx,
You are so right, they will all work.  One needs to choose a method that suits you, or appeals to you the most.
Personally, I abandoned the distribution grid idea about 4 years ago believing it to be a waste of time, nothing wrong with that method but I did not like the need to clean the pipes fairly regularly.
I believe it would be a necessity to have a grid distribution if you were running continuous flow.  Others may have found differently.
We sometimes build timer based flood and drain systems when clients ask for them, and they work wonderfully.

I guess I just like the beauty of auto siphons.  They work so well and I believe carry with them some advantages as listed above. IMHO

Yep Murry, it does definitely depend on situation and personal choice as to what will be best.

 

I do like auto siphons and my original system ran mostly on loop siphons.  I like that siphons allow for continuous running of the pump and skip the timer issue, however, you can't depend on siphons to "always" run randomly or perhaps it's more that their random nature tends to mean that occasionally they may all flood or all dump at once and therefore the fish tank or sump tank still has to be big enough to handle all beds flooding and draining at once even if it might not happen often.

 

However, in order to operate with a smaller sump tank but still have a large amount of grow bed volume, I had been using a sequencing valve and discovered the benefit of intermittent inflow to the bed decreasing/eliminating the issues I'd been having with the "sliming" of the gravel around the single water inlet. 

 

I actually like the combination I'm running on the big system lately though that system having grown, changed, grown changed etc isn't something I would try to "sell" to anyone since it's probably too confusing.  It does let me test out a variety of things though.

I have been running a permanently on system in various configurations since late 2008 on the same pump.  It was not a very expensive pump either.  I think some of the theories of plants wanting to have intermittant dry spels are wasted on me, as I have always set a system up to function optimally for me in terms of water turn-over and electricity usage, which means the plants get what they get.  That said, I have been monitoring a tomato plant sitting in a raft tank that is actually bigger than his counterparts planted in flood and drain beds at the same time.  I don't think he got the memo.....

 

I like many of the arguments put forward here about the usefulness of always on flood-and-drain, although I am also the kind of person who believes that there are many good methods.  I use my water pump as effective earation as well.  Raised flood-and drain auto siphon gravel beds are central to my design.  I get good water turn-over (I also come from the "turn your system over at least once per hour" mindset), good aeration and good fines removal all from one single pump.

 

Perhaps what people can try to develop for indexing valves is to have a pump that is always on (to make it last longer), but a timer valve that opens a smal diversion to the main line that will allow the cam to kick in and the indexing valve to rotate.  I'll leave it to my engineering friends to see if their is a very robust and reliable way to do this.

Kobus, TCL has done some work with "Chop" based, continuous pumped systems and the indexing valve...

 

The indexing valve merely requires an interruption of flow to sequence, and methods such as a solenoid or flout are sufficient to trigger the sequencing...

 

With regard to the BYAP trials,,, firstly I'm absolutely sure that Joel has been completely faithful in reporting the trial without riding the "horse" in any particular favour or direction... to suggest otherwise is I think inappropriate...

 

Secondly, I must admit that I'm somewhat surprised as to the performance of the constantly flooded system....

 

In my experience I've not acheived comparable results, and I'm not a fan... but others have had satisfactory results....

 

The significant objection to timer based systems seems to be the possibility of timer failure, and I have had a timer fail... after about two years of operation.... and a recent bad batch of made in China timers... has resulted in myself, (and BYAP) changing brands/models...

 

But I've also had pump/siphon failures....

 

In terms of water quality.... I've yet to see any issues in a properly configured timer based system.... nor have I had the need to "clean out" the distribution grids...

 

As has been said, there's more than one way to skin a cat... and if it works for you,,, go for it...

All I can report is what I have, as I do not have a timed system to compare to the always on flood and drain with auto siphons that I use.  All the pictures of my crops were obtained from that system.  While the tomato is going crazy in the raft, some other plants like the gravel better, although nothing, apart from one batch of cucumbers, have refused to grow in the configuration I use.  I currently have 25 different plant species / cultivars going in the permanently on system.

RupertofOZ said:

Kobus, TCL has done some work with "Chop" based, continuous pumped systems and the indexing valve...

 

The indexing valve merely requires an interruption of flow to sequence, and methods such as a solenoid or flout are sufficient to trigger the sequencing...

 

With regard to the BYAP trials,,, firstly I'm absolutely sure that Joel has been completely faithful in reporting the trial without riding the "horse" in any particular favour or direction... to suggest otherwise is I think inappropriate...

 

Secondly, I must admit that I'm somewhat surprised as to the performance of the constantly flooded system....

 

In my experience I've not acheived comparable results, and I'm not a fan... but others have had satisfactory results....

 

The significant objection to timer based systems seems to be the possibility of timer failure, and I have had a timer fail... after about two years of operation.... and a recent bad batch of made in China timers... has resulted in myself, (and BYAP) changing brands/models...

 

But I've also had pump/siphon failures....

 

In terms of water quality.... I've yet to see any issues in a properly configured timer based system....

 

As has been said, there's more than one way to skin a cat... and if it works for you,,, go for it...


Murray, What indexing valves did you use on the job that you reference below???


Murray Hallam said:

We have also built and commissioned a 20 grow bed system (150 gallon beds) using a timer, sequencing valves and large capacity pump.....also works really well. 
I can expand on how these two systems compare if anyone is interested.

Just sent you a email John.

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