Backyard Aquaponics
A place to discuss aquaponics

Hi,

Is there an optimal flood-drain time? For my new system, the pump will take about 20minutes to flood the grow beds. If the fill time is 20minutes, can the empty time also be around 20 minutes, or is it best to have rapid auto-siphon? Is there a maximum flood time /drain time?

Thanks
Rob

Nope, whatever works. 1 hour to fill, 1 minute to drain is fine, or anything inbetween.

The ideal is to move all your tank water every hour. If that can be achieved with a 20 minute fill, then all is good.
Drain can be as long as you like, there are both fast siphon activated flood and drain as well as 'slow drain' systems. (slow draining requires a timer usually)

There is a belief that the faster the drain, the better, as this aids in oxygenating the roots and water, but slow drain has been proven effective also.

Great question. So, I need to flood my grow bed every hour? 24 times a day?

you'll need to let me know your GB sizes and FT size for me to answer that. I know it's probably in your head, bu they, I'm an Engineer, I'm too damnably lazy to research

Ok cool, Thanks!

I'll size my pipes for fast drain, so if I find slow drain auto-siphon isn't working too well, i'll move to fast auto-siphon.

Cheers
Rob

Hi KP sorry been gone so long. Troubles with no 1 son have kept me from building system.
Q is it appears that some vegies - chilli and toms etc like a reduced amount of wetting of roots
So i am thinking that twice per day for those and yet green vegies 1 / hr
To do this and keep it simple that is the question how?
Has anyone done some timing on how long it takes a growbed of known volume taking account of say 40% substrate (gravel or clay balls) to siphon using the various standard (bunnings) sized tubes? eg how long does it take for 1m^3 of water to siphon through different sized commercial tubes?
You being an engineer and all I am happy to see a formula provided there are only commonly used variables.
regards
Aquam

Dont know where you got your info but i have had chillies and tomatoes growing in scoria, vemiculite , crushed rock , at times from 3 min fill 50 min drain to 15 min fill 2 hr drain the one in vemiculite did extra well this year so there in my book there is no hard and set rule

My chillis grow well but I never get round to eating them.

+1 ....I agree with F&F. I have had my GBs flood&drain 2x in 24 hours. No difference.

When you are cycling then you have to F&D more often

Personally, I don't think it really matters so long as you are flooding and draining. However if you only flood briefly a couple times a day, your fish will probably suffer from the lack of filtration unless you only have a few gold fish, in which case it will take quite a while to build up enough nutes for stuff lime tomatoes.

I'm growing Tomatoes, hot peppers (hungarian hot wax, cayenne, jalapeno, habanero) and they seem to be doing fine with my constantly filling and auto-siphoning beds. I think most of my beds flood and drain at least twice per hour. I have lots of composting worms in my beds to help keep the solids under control. Just make sure there is a good dry layer of gravel over the top that never gets flooded, this helps avoid root and stem rot. I have noticed that a tomato plant right next to the inlet of a bed, if the water starts backing up over the gravel by the tomato, that tomato did suffer because the stem right at the surface was constanty wet and the area around it's roots probably never drained well in the flood and drain cycle. The tomato a foot further away from the inlet did just fine.

Great, Thanks for the replies.

TC, to avoid the problem of the stem rot, would you recommend that the input pipe distributes the water around the entire bed, rather than just concentrating the water in one place? The GBs I'm going to use are quite large, 3m2 surface area. Are sprinkler heads an option, or is it best to keep the water off the plants?

Thanks
Rob

I can't grow tommies , and my chillies and capsicums grow in scoria with 15 min fill 10 min drain continuous flow siphons.

Fill/drain at a rate that will prevent drowning/root rot and will also prevent roots from completely drying out.

Cool, thanks. I'll keep that in mind.