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  1. #1
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    Newbie Question: Cycle Time

    I've a burning question regarding the cycle of my ebb and flow system in my mini scale aquaponics set up.

    I understand that ideally I want at least 4 cycles within an hour, however, my cycle from flood to drain is 1min 40 sec, which takes me over 30 cycles an hour.

    Is this too much? What consequences are there for too much cycling?

    I've tried to bring the number down by decreasing the input of my water, but by doing so my bell siphon doesn't kick start at all.

    I would appreciate anyone with any input on the matter.

    Thanks in advance.

    ****************UPDATE: August 28******************

    Since our last conversation, I've kept my system at 1min 40sec cycles just to see how it goes and yesterday I discovered some mold growth at the base of my plants and on the clay pebbles surrounding them. I figured it was all that constant moisture I was giving it so I decided to wipe off the mold and repipe my water output with a smaller tube. Now my cycle time is 6min 20sec which gives me about 9 cycles/hour. Yay!

    On an unfortunate note, I was extremely careless while cleaning my tank and making all the system changes that there were 2 guppy fry casualties. No bodies found yet, just missing. I'm crossing my fingers that they are still alive somewhere
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  2. #2
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    Re: Newbie Question: Cycle Time

    Very frequent cycling will increase your disolved oxygen, and keep your plant roots wet. This may an issue depending on what plants you have. You should read Oliver's 101, which has a lot of very good, detailed information on AP, and I'm sure others will chime in with their feedback.

  3. #3
    Members Aloha Don's Avatar
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    Re: Newbie Question: Cycle Time

    Instead of a bell siphon have you considered having a drip system on a timer?
    What is the size of your auto siphon? Height of your standpipe?
    As you may know, you want to keep the top of your grow bed to stay dry.
    Can you raise the height of your standpipe?
    Do you have an air stone in your fish tank?
    Put all excuses aside and remember this: YOU are capable - Zig Ziglar

  4. #4
    Members dead_sled's Avatar
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    Re: Newbie Question: Cycle Time

    You could add a spray bar to divert the excess pumped water back to the FT. This will add oxygen and increase cycle time.
    Less irritating avatar since 02/27/14.

  5. #5
    Aquaponics 101 Oliver's Avatar
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    Re: Newbie Question: Cycle Time

    The reason you are cycling so often is that your siphon is rather large for the size of your grow bed. The siphon you have designed has about a 2:1 timing range. As you have noticed as you adjust the water flow the timing changes until you bump up against the limits of that range. In order to increase your time you will need to reduce the size of the stand pipe. This will decrease the rate at which the water flows out of your grow bed. You will also need to decrease the inflow as well so as not to go beyond that new limit.

    As in most things in aquaponics, there are differing opinions about how things should be done. I would say that cycling as fast as you are is probably too fast, as it does not allow for the moisture that is retained by the media and plant roots to have time for the oxygen in the air that is drawn in during the drain half of the cycle to fully penetrate that moisture as far as it otherwise could.

    In using our PinPoint DO meter, calibration requires placing a film of moisture on the probe tip and allowing the oxygen in the air to be absorbed into it. It takes only a few minutes for it to fully saturate that thin film as the meter changes and then stops changing. That is an indication of how long it takes for the air to saturate the moisture left behind on the media and roots.

    So, I would say a 5 to 15 minute cycle would be about the range you would want to design into your system. Anything less than 5 minutes and the aeration of the grow bed may not be complete. Anything longer than 15 minutes is decreasing the amount of nutrients that are presented to the plants and the media where the bacteria do their work and require lots of oxygen and waste to be processed.

    Having said all of that, I am of the opinion that if you have enough dissolved oxygen in the fish tank water, then all the above doesn't really mater.

    Again, this is just my opinion and I will admit that I am shooting from the hip here.

    Oliver
    To measure is to know

  6. #6
    Members bsfman's Avatar
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    Re: Newbie Question: Cycle Time

    Why not just go with what you have and see how it works? It's not like you have a massive crop at risk in a mini system.

    True, your water will have less contact time with the nitrifying bacteria during each cycle, but it will have more frequent contact with it which should even out in the long run. I would think the more frequent cycling would also increase the oxygenation of your water which is good for your fish.

    If you do decide the fast cycling is having an adverse impact on your plants, rather than re-plumbing your stand pipe and siphon apparatus, you could always get a cheap timer and set it for 15 minutes. That way, you would have 8 or 9 cycles for 15 minutes, then a 15 minute "rest" period. This would probably give you the same effect.

    But try it first as is. Modifications may prove unnecessary in labor and expense.

  7. #7
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    Re: Newbie Question: Cycle Time

    Wow, I'm really happy with all the responses here and super happy that I joined this forum. Thanks eddiemigue for directing me to Oliver's 101. I've been reading on it, and have yet to read enough to find my answer but I found a whole goldmine of useful information.

    And thanks Oliver for personally posting your opinion and such detailed help. I think you're right that my siphon is too large, that certainly makes a lot of sense to me now. Ideally, I should correct that but bsfman gave a great idea with using a timer and just go with it and see how it works without correcting the standpipe. Should I be scared of getting root rot from too much exposure to water?

    Aloha Don mentioned that I should keep the surface of my grow bed dry, I didn't know that. What is the purpose?

    FYI:
    Planter height: 5"
    Grow bed height: 4.5"
    Standpipe height: 4"
    Water input diameter: 3/8"
    Siphon output: 5/8"
    Yes, air stone in tank

    I could probably raise my stand pipe a little but it would make nominal difference in cycle time.

    I'll go ahead a try the timer, if not, I guess as long as I have sufficient dissolved oxygen, there can't be too much of a problem.

    Thanks guys


  8. #8
    Members Aloha Don's Avatar
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    Re: Newbie Question: Cycle Time

    When the top of the GB gets wet which is exposed to light, it can create an environment that algae can thrive. This is not beneficial to plants or fish because the algae use up oxygen which plants and fish need.
    Put all excuses aside and remember this: YOU are capable - Zig Ziglar

  9. #9
    Members bsfman's Avatar
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    Re: Newbie Question: Cycle Time

    Quote Originally Posted by Xine
    Should I be scared of getting root rot from too much exposure to water?
    Probably not. I successfully grew tomatos and carrots in two grow beds that cycled every 2 minutes and had no problems with either. Even on a 15 minute cycle, your plant roots never get dry. I really think you will be okay. See what happens and adapt if necessary.

  10. #10
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    Re: Newbie Question: Cycle Time

    Thanks bsfman. It makes me more at ease knowing you've got some success with just 2min cycles.

    Aloha Don, your info helps a lot. I've been meaning to clean my tank but figured I'd hold it off here and there (lazy). I've lots of algae on my glass and didn't think it'd do any harm but knowing now that they rob the oxygen, I'll get rid of it ASAP.

    Thanks!

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