flood and drain intervals

[jillswindoll]

I am going to be intentionally vague to start with...

How do you decide what your flood and drain times and intervals should be?

Thanks a lot!!

[Hamish]

I didnt decide - it just turned out that my grow beds take about 10 - 15 min to fill and about 1 min to empty via the auto siphon.

[jillswindoll]

My system runs for a total of twelve minutes: the bed takes three and a half minutes to fill and twelve minutes from the time the pump kicks on until the bed is all drained. I have a timer that lets me program 20 events per day so I can run it every 72 minutes.

How do you know if the water is staying in the bed long enough for the bacteria to convert the ammonia and the plants to take up the nitrates? I ambient and water temperature, how often you feed your fish, what kinds of plants you are growing, blah blah blah!!

I test for ammonia, nitrites, nitrates (all zero) and although my water looks like pea soup the fish seem very happy. I have been cycling the system for about a week and I want to add plants to the grow bed. I have looked all over the internet but I don't see a "rule of thumb" for how long and how often to flood and drain.

Thanks!

[Murray]

I don't think that the interval is all that critical. I have some systems that flood and drain over about 12 minutes. They are doing great.
I have another system that floods for 5.5 minutes and drains for 50 minutes. It is doing great.

Get some plants in there asap. If the plants are not doing so well add some Seasol (seaweed extract)

[Outbackozzie]

I have a system that floods, then stays drained for 6 hours at a time - no problems.

I have a system that stayes drained all the time - no problems.

As long as water is circulating enough through the growbeds there will usually be no problems.

[jillswindoll]

Thanks, guys! I will get some plants in there tomorrow!

[bushboy]

Good question - I don't know the answer either.
My setup - my pump would fill my grow beds in very short time if I didn't
bypass some of the flow back into the fish tank

I currently have 30mins off and then my grow beds fill in 1min 20secs
and then promptly drain back to my gb (autosiphon) - all over within
another minute or so.

Plants doing fine, water chemistry ok - water is a bit murky though

I suspect I could cut back my time off further and will slowly try this
as it would mean less electricity used.

I had looked for an answer to this when I first setup my system
and was told, or saw somewhere, that cycling every 20mins was the go
but have since seen multiple cycling times that are quite different to this!!

Maybe there is no hard and fast answer - being of analytic bent it would
be nice to be able to say - gbs needs to fill X often/hr and drain @ Y rate
determined by a,b,c chemistry or some other measure

[Murray]

Hi Tom, I don't think there is any real knowledge on the subject for anyone to be firm about the best cycle time.

I "feel" that anything less than about 15 minutes might just not be good in the long term. Once again I really don't have any evidence for that, just observation. The single bed Balcony kit does not get the same remarkable results as the 3 bed kit. The same pump is used in both kits, so the cycle time is longer in the 3 bed kit. about 20 minutes.
But the other variable that may make the difference is the grow bed to fish tank volume. On the one bed kit the ratio is about 1/3 grow bed to 1 fish tank.....On the three bed it is much closer to 1 : 1

[Dufflight]

although my water looks like pea soup the fish seem very happy.

I used air con filter under the inlet to the GB. After a couple of days the Pea soup went, then I could see the bottom again. Added a little peat to the bio-filter to drop the PH and ended up with pea soup again. Need more plants.

[Outbackozzie]

If your water is murky you need to increase your amount of pumping. At the point that the water is clear, and readings are good, is the most efficient.