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.

[Dufflight]

Once I get all the GB's online it should help. Then there is the solid removal tank that could be fun to play with. Even if its only used to vacuum the bottom.

[GaryD]

Hi.



.....and ended up with pea soup again.

"Pea soup" water is the product of nutrients and light. Cut back the feeding and cover the tank (if possible) and you'll resolve the problem. Watch your pH......algae blooms may cause rapid shifts.

Gary

[Outbackozzie]

The algae will consume a lot of the available oxygen in the tank as well, so extra air has shown to be helpfull in getting the system back to clear water.

[jillswindoll]

I used black landscape fabric to cover my tank almost all the way...the only part exposed is where the water returns to the tank, and I have rigged some shade for that part. I added an extra pump and filter to increase O2 levels and help get rid of some of the algae. I have already cleaned the filter out once--it was jam packed with green crud but I am not sure it is going to help me much in the end. I think it is very helpful with adding extra O2, though. I have not fed the fish in two days so hopefully all of these small steps will add up. I will check the pH this morning and keep an eye on that as well (thanks, GaryD!).

Dufflight: Did you say you use an air conditioner filter? I had considered that but I wasn't sure if it would leach any unknowns into the tank. I'll have to give it a try!

Murray, you said that "anything less than about 15 minutes might just not be good in the long term"...do you mean the total amount of time it takes for the bed to fill and drain, or do you mean you shouldn't allow more than 15 minutes before another flood and drain cycle starts (four times per hour, 96 times per day)?

Thanks for all of your help!

[Murray]

Murray, you said that "anything less than about 15 minutes might just not be good in the long term"...do you mean the total amount of time it takes for the bed to fill and drain, or do you mean you shouldn't allow more than 15 minutes before another flood and drain cycle starts (four times per hour, 96 times per day)?
I mean, the total time for the bed to fill and then drain. For a complete cycle.

For me I find that about 15 minutes is good as a minimum.

We have a new kit that we are running on test at the moment and it varies a little at around 15 minutes complete cycle. It is going great.

The Solar Ready kit has a 1250 ltr fish tank, 2 x 450 ltr grow beds, a 450 ltr sump and a 250 ltr fingerling tank. Around 1800 ltrs of water in use with 900 ltrs of grow bed volume. All run on a Solar Ready pump drawing only 40 watts.
With a grow bed to fish tank ratio of only 1/2 to 1 it will be very expandable in grow bed capacity. I will be doubling the grow beds this coming week to see how it goes at a ratio of 1:1 I have no worries re nutrient availability. The pump capacity will be the issue, and the long term effect that will have on nutrient/water distribution to each grow bed..