Backyard Aquaponics
A place to discuss aquaponics

I am about to setup my growbed and I was going to use an auto-siphon but some recent posts are making me wonder if simple timer and drain is better, is there any consensus on this matter? What are the pro's and con's of each?

I don't think it's really a matter of one being better than the other. Running a timer probably makes easier to get the siphons working. If you do run a timer, it's easy to get the siphons set up. Just use a siphon tube size that will drain the bed before the next batch of water comes along.

I don't think one is better than the other. Each has benefits and drawbacks.

Siphon pros,
automatically drains bed when it gets full
you can run pump constantly providing extra aeration
smaller pump running continuously
each bed can flood and drain on it's own schedule
splashing of siphon water returning is good aeration

Siphon cons,
balancing inflow/outflow rates can sometimes be tricky
Sometimes it can be fiddly to get a siphon to consistently kick in or kick off
sometimes a siphon not kicking in properly will leave a bed flooded long term
sometimes a siphon not kicking off properly will leave a bed mostly drained long term

Timer/slow drain pros,
easy to program
(so long as you keep the drain stand pipe accessable to adjust holes, it is easy to adjust drain time)
a powerful pump doesn't need to run all the time, saving power

Timer/slow drain cons,
timers can fail
may need extra aeration aside from the pump since it is off most the time.
need to find a timer with a short enough cycle time for filling the beds.

You decide.

A smaller continuous flow pump can also be used with a siphon setup, whereas a larger pump is used with a timer and a large volume of water is pumped in a short time

There is many ppl on either side of the fence and each point out there setup is best in a friendly sought of bragging way...I have my systems using small continuous flow pumps:
- one has bell siphons which have been running for over 18 months efficiently
- the other has actuator valves to divert water to single consecutive GBs (6 of 500 litres each) that has been running for over 12 months from memory

Joel has used the timer method from the beginning as I understand it and he hasn't reported (m)any malfunctions...copped lots of flack from the better performing continuous flow systems tho

..as TC pointed out

I have burnt out too many pumps over the past 2 years with continuous flow (the pump running 24/7), so I am going over to flood and drain. I also use small diameter in my loop auto siphons, which have become blocked with debris, (which lead to GBs overflowing), or build up a thick layer of bio-film, which in effect reduces the diameter of the siphon pipe - this has resulted in overflowing beds too - simple maintenance would have prevented this but I tend to forget. I guess I am trying for a system which is idiot (AKA me) proof)

In the auto siphons I have used the bed does not have a long enough 'dry' period for me... I am now thinking of a 15 minutes on, 1 hour off cycle - as I will have more GBs soon enough this will be plenty to cycle my water...

But it does come down to what you are comfortable with, so go with your gut

Autosiphons (bell siphons particularly) have massive "Cool" factor. I love the idea of them, and they work fantastic (no moving parts etc). But they're a bugger to set up compared with ye ol' standpipe and timer.

I was going to have autosiphons, but the standpipes were just so damn easy that I ended up doing them just to get the system going. So really, it depends on if you want it to be cool or not =)

My big system siphons, are now a 'fill at pump startup, drain, and stay drained until the pump next turns off, and restarts.'
Essentially a flood and drain, continuous flow system

I like that the siphons, flouts, sump pumps, drain a bed quickly providing the big splash and moving water factor. But since my pump runs continuously, the beds do not get a long period of dry time. So far it doesn't seem to be drowning any plants though of the 6 Rosemary cuttings only one is still surviving.

TC I had no luck with either Rosemary or Thyme in my AP system. I haven't yet checked to see the optimum conditions for Rosemary. Thyme likes it pretty dry and I suspect Rosemary may also like it that way. On the other hand, have you tried lemongrass yet?

Simillarly my rosemary is suffering, however I feel it would suffer in a slow drain as well as my autosiphon continuous flow... unless of course the bed was allowed much longer 'dry spells' which would probably result in half my bacteria carking it, and of course those plants sharing the bed who are loving the water...
I know it's been said before but beware mint. I planted a peppermint last year, and it seemed it hadn't grown... only it had, just that it was a little below the surface of the scoria... 4 times as big as it seemed on the surface! I still don;t know how it was getting enough light.
Hmmm I think I may be a little OT here.

Dont worry about the bacteria carking it recently my beds had no water for 36 hrs with no problems

Aquamad mentioned a problem with pumps, I was under the impression pond pumps were designed to run 24/7 and it was a problem to switch on and off all the time. I was planning continuous pumping for the water flow and air for trout.

Since I just got my pump I think I will probably go with serial filling of the beds fed by part flow from the tank overflow. My original thought was that siphon would create more aeration than slow drain but maybe faster filling achieves the same result.

With the wrong pump you can have problems.
Pumps not able to cope with the particulates tend to place a higher load on the motor, and therefore die.
Pumps run at or close to their designed pressure also wear faster.
with pumps, bigger is better.
Restricting the output is more highly recommended than restricting the input, however diverting water back into the tank to reduce flow is by far the nicest for yout pump, and you get free aeration too :-)

Different pumps have different designs and uses.

A pump designed for continuos use,,say a sponge filter power-head should lastfor YEARS doing that task. My Rio power head has run 24 hours a day 7 days a week for over 10 years. 10 years of almost nil maintenance (impeller got clogged once about 3 years back), pump under duress,,,yep I don't clean my sponge filters often.Thissamepump wouldprobably not like to be switched on andoff on a regular basis.

Choose a pump designed for the task,,don't buy cheap,,and always get bigger than you think you need.