James Blythe

Concept for chift-pist - somebody stop me before I hurt myself!

7 posts in this topic

I have read published research that recommends two important goals of a bya system:

  • the water in the fish tank needs to be cycled/replaced every half hour, and

  • the nitrifying bacteria in the growing media need a little over half an hour to most efficiently process the fish effluents.

Common sense gives us two more goals:

  • one of most important factors to bya enthusiasts is the cost of building a system

  • another factor, especially to newbies, is the skill levels needed to assemble and operate a bya set-up.


  • materials and tools must be inexpensive and readily available,

  • skill requirements to construct and to maintain the system must be minimal,

  • fish tank cycling goals are in half-hour increments,

  • grow bed flooded cycle goals are also in the half-hour range.


Scouring the internet, I cannot find even one system, anywhere, that meets all four of those goals. Bya systems that accomplish the first two, even the first three, of them are everywhere. Mr. Hughey's Barrelponics, though not a chift-pist system, is an excellent example of them. But that last goal... to accomplish that one seems to require negating at least two of the other desired criteria, if not all three.


Let's use a standard chift-pist system as our basis: fish tank, sump tank, and multiple media-filled growbeds. One pump in the sump tank pushes water up to the fish tank, which overflows, gravity feeding the grow beds by way of some kind of distributive manifold, the grow beds flood, then gravity drain into the sump tank, most commonly initiated by either bell siphons or toilet flush valves/counterweights in each bed. The system is simple, easy to assemble, fairly easy to maintain, and with the proper pump it meets the first three of our goals - but not the last one.


Neither bell siphons nor toilet flush valves allow the water to 'steep' in the grow beds for any length of time. As soon as a bed fills, it drains. (Assuming the bell siphon isn't being cranky today or the weep hole in the toilet valve counterweight isn't clogged with algae.) Let's just ignore the fact that the drain mechanism takes up precious room in the grow bed – room we could use to raise another tomato plant. The bacteria colonies driving the system only have a short time to work their magic on the effluents in the water before it is whisked away. The bacteria closest to the growing surface have practically no time at all, in fact. It's like they were being served at a restaurant only to have the waitress take their plate away before they are finished eating. And the water, still containing significant amounts of effluents the bacteria didn't have time to process, is returned to the fish tank, inadequately scrubbed. (And people wonder why they have so many problems with algae!)


Which brings us to the flaw in using bell siphons or the like to drain the grow beds. These devices, besides being rather moody and requiring constant attention, are only capable of taking one input: the water level of the bed they are in. They cannot be triggered by anything else and they cannot be intentionally delayed in their task. They are passive devices.


Some people use a timer to turn the pump on and off at some preset interval. But without real-time input from the growbeds, and considering all the constantly changing variables in the water flow, timers are far from being precise. And constantly shutting down and powering up the pump makes it wear out faster. Even more importantly, it interrupts the critical flow of water through the fish tank.


I have seen one instance of a very clever fellow who devised a way to direct the flow from the fish tank to each bed in turn. He used a motorized cam to "pinch off" all but one flexible supply line, and a timer to rotate the cam to the next position, this allowing him to fill the grow beds sequentially rather than concurrently. Unfortunately, the pictures I saw were of pretty small supply lines – in the 5/8" to 3/4" range. Certainly not large enough to handle the output of even a medium sized pump, or to supply relatively large grow beds. This scheme is a step in the right direction, but still doesn't address the issue of "steep time" for the grow beds. If memory serves, he was employing bell siphons to drain the beds in his system. His grow beds, save the one being filled at the time, stand empty until their turn in the filling sequence. This is the exact opposite of our goal.


So how, then, do we accomplish all four goals? How do we devise a way that is simple, practical, affordable, easily understood, constructed, and maintained, keeps the fish swimming gaily, and finally give those poor bacteria a chance to eat their fill?


Bear with me, please, while I conduct you through a little fantasy:


Posit a chift-pist set-up with 8 grow beds, each displacing 1/5th of the fish tank capacity. Number the beds 1 thru 8. Our system is sized so that it takes 5 1/2 minutes to fill a grow bed and 2 1/2 minutes to drain it.


Now, let's click on a stopwatch:


00:00:00 - Picture grow bed #1 just beginning to fill, bed #2 drained, and beds #3 through #8 filled with water. There is a man behind the curtains over there, nodding off as he waits.


00:05:30 - #1 finishes filling. It magically signals The Man Behind The Curtains (TMBTC) of this fact. TMBTC springs into action; closes the drain to #2, opens the drain to begin emptying #3, and redirects the flow of water from #1 to #2, all in the space of about a second and a half. Seriously. A second and a half to do all that.


00:11:00 - #2 signals TMBTC that it is full. TMBTC pulls his levers, closing the drain from #3, opening the drain for #4, and moving the flow of water to #3. #1 has now been 'steeping' for 5 1/2 minutes.


00:16:30 - #3 is full. TMBTC opens #5, closes #4, and moves the flow to it. #1 has been flooded for 11 minutes.


00:22:00 - #4 is full. TMBTC shuffles things to the next state, opening #6, closing #5, and moving the flow to it. #1 has 'steeped' 16 1/2 minutes.


00:27:30 - #5 is full. #6 closes and begins filling, #7 drains.When #7 finishes draining, it will have been the fifth bed to do so. Since it took about 2 1/2 minutes to drain, that means that the entire contents of the fish tank have been replaced in almost exactly 30 minutes. The fish are happy. #1 has steeped 22 minutes. TMBTC goes back to sleep until called again.


00:33:00 - #6 is filled and wakes TMBTC to shuffle things along to the next beds, #7 and #8. #1 has been flooded for 27 1/2 minutes.


00:38:30 - Thirty-three minutes after #1 filled, it drains. It will stay drained for 8 minutes (long enough to air out, not long enough to dry out) before it begins filling again. The bacteria are very happy.


00:44:00 - The entire cycle is complete and back to it's original state.


[side note: We can radically alter the 'steep' times of the grow beds by simply changing the beginning state of the grow beds. The example I just walked through had all but one bed filled – by starting the cycle with more than one bed empty we can alter the steep times without affecting the fish tank cycle time or flow rate of the system. In fact, if all the grow beds started off empty, we would essentially have the same situation as a "standard" system: each bed would drain immediately after it filled. But it would stay drained until each of the other beds had also filled and drained in their turns – in this scenario, almost 40 minutes.]



I can build The Man Behind The Curtain. Granted, it's a little more complex than a normal chift-pist set-up, but not over much. And it's a little more expensive, but not exceedingly so. The mechanics and principles behind the idea are simple and forthright. No timers, no arduinos, no expensive seqentual valves, no fancy sensors or micro-switches; just simple everyday components re-purposed and assembled in a rather unique way, and a bit more pipe. Everything necessary in the way of materials can be purchased in one trip to the local big box merchandise store, big box hardware store, and an autoparts shop. Many of the pieces could be scavenged from a junk yard. Only one part needs more than modest fabrication. Even then, a serviceable one can be cut from a plastic chopping board by someone with a steady hand and eye, using their jig-saw and electric drill. The most arcane component is a basic automotive relay that can be purchased new at any autoparts store for less than the cost of a double cheeseburger and fries. The single most expensive piece in the entire assembly cost me less than $50 new. I'm pretty sure I can put the whole thing together for well under $300.00.



The question before the house is... Do I want to?


Is it worth it? Would it make a significant improvement in the efficiency of a bya chift-pist system? I, in my ignorance, think the answer to that might be 'Yes' to all counts. But what do I know? I'm not an expert at anything, just a dabbler. Many of you on this forum have vastly more knowledge and experience than I do. What's your opinion?



I really wanted to come up with a catchy name or acronym for this contraption. "Hydra", "AquaSpyder", something like that. But, alas, anything I dreamt up was already trademarked, or just too pretentious. I privately refer to it as "my Hydra tower", but that's simply because it's easier than calling it "my RubeGoldberg-esque Mechanical Man Behind The Curtains Aquaponics Control Tower".


JB, September, 2014

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You might find some that would be interested, but I find it hard to believe that anyone that serious about optimum cycles for nitrification, and fish growth would use media beds as the primary means of nitrification.  A filtration system with moving bed bio reactor (MBBR) would eliminate the need for retention times in the grow beds and allow the grow beds to be cycled through what is optimum for plant growth. 


What you describe is one way of doing it , and an admirable attempt to solve a problem, but there are better DIY systems available that just perform much better and remove constraints such as auto siphons and timers.

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Thank you for your response, Ravnis. I can see that I have a whole lot to catch up on! My intent was to come up with something that any dummy - like me - could put together in his back yard without spending a fortune or having to rely on hard-to-get parts/materials. I must confess my ignorance, yet again. I have never even heard of a "moving bed bio reactor"! Any chance you could point me at a DIY/backyard sized example of one? 


Thanks again,


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James, a very simple solution exists for your scenario... and costs less than $100...


It's called the "aquaponics valve"... a sequential indexing valve specifically designed for aquaponics...


It comes in 4,6, and 8 port models.. in various pipe sizings...


The valve is sequenced by interruption of flow... by a timer... and utilises a traditional timed flood & drain overflow standpipe...

rather than siphons... which results in a "slow drain" (user adjustable)


It can deliver flow for a timed period to single grow beds, or grouped banks of beds... in sequence...


Or deliver banked outlet ports to single, or banked groups of beds.... (the options are numerous)


I have "flash" files available that show how it works... but can't attach or imbed them here


You can see them here ... (must do some work on the site lol)....



Edited by RupertofOZ (see edit history)
James Blythe likes this

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Jim: Just came across your post a bit late and I am wondering if you are still pursuing the concept. A year ago I could not offer a solution but now, due to a recent development, can. It would do exactly what you want without timers or power and use a foot or less of head. Only one pump is needed. If you are still interested contact me! Jim

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