C.H.O.P Operating System. Notes and comments, How does it work?

It is most interesting to see the amount of traffic to our site that has interest in CHOP Operating systems. Daily I receive emails from all over with questions and comments about CHOP 2 in particular. In this blog, the pages and posts regarding CHOP 2 are the most read.

I derive a great deal of satisfaction and pleasure in seeing the many hundreds of CHOP 2 builds happening. Everywhere, folk are using IBC's (Totes) and getting into Aquaponics. There are lots of ways to use IBC's in the construction of an Aquaponics system.

We have been running CHOP 2 systems for well over 18 months, one system being a medium sized commercial build we carried out (combined raft and media system). So we KNOW it works and has many advantages especially in the plumbing department.

If we consider CHOP 1, the water is pumped from the sump back to the fish tank and that water then runs back to and through the grow beds by gravity from the fish tank. The water comes from the bottom of the fish tank, up and out then down to the grow beds. This has obvious benefit of keeping the fish tank always full no matter what. CHOP works better if the pump is up sized just a bit to make sure there is good flow of water through the FT in order to lift the suspended solids up the standpipe and out down to the grow beds or sump. This is much more easily achieved using CHOP 2 because we can pump a lot more water through the FT and back down to the sump by gravity. Meanwhile the grow beds are doing their thing processing the water.

Aquaponics Fish Tank

Water is bypassed back to the fish tank to provide good water movement and additional aeration. See the duck weed in the fish tank.

Many AP practitioners operating CHOP 1 bypass some of this extra capacity back into the sump to provide aeration in the sump. (remember the pump is in the sump not the FT) In much simpler non CHOP systems where the pump is in the fish tank, and water is pumped from the fish tank directly to the grow bed, the extra pump capacity is bypassed back to the fish tank to create water movement and aeration.
The volume of water that can be processed through the grow beds is limited or regulated by the auto siphons, or in the case of a timed system, by the timed pump cycle. The filtration action is being carried out by the grow beds and they are processing the amount of water that is delivered to them. They cannot process any more water that can be passed through them. (obvious I know)
All we are doing with CHOP 2 is delivering excess pump capacity back through the fish tank again, creating a second loop if you like. The water being sent back to the FT will be partly filtered, partly not. All the water in the system will pass through the grow beds (filters) at the rate the grow beds can handle the volume of water and be filtered no sooner or later than it would have been anyway. In the meanwhile any additional pump capacity is being used to circulate water through the fish tank making sure that the suspended solids are being lifted from the bottom and sent to the sump.

Some have made the comment that the solids are being munched up and sent round and round, hurting the fishes eyes and turning into soup. This paints a picture of great big lumps of fish poo out of control banging around in the system. This is just not true. If you have that much fish poo in your AP system best you quickly lower your fish population, feed less, add more grow beds or add some serious filters ASAP.
Fish do well when there is a lot of water movement in the FT...they love it.

CHOP 2 Aquaponics

CHOP 2 with external drum filter added. It is easy to add or subtract additional elements to a CHOP 2 system.

It is assumed that there is no additional solids filtration in the system anywhere, other than that provided by the gravel grow beds. To add a stand alone solids filter of some sort is very easy using CHOP 2 methodology. Simply create another loop in the system and/or deliver water from the pump (in the sump), to the filter then on to the FT, or on to a raft bed then back to the sump or FT. All that is requires is a few more fittings and some pipe and job is done. You can disconnect or reconnect the filter easily for servicing, or add or disconnect additional raft beds if you want.

Or, add a filter between the sump and fish tank. Interrupt the water coming from the sump pump back to the fish tank. Once again, very easy to do in a CHOP 2 system. You may need to up the capacity of your pump a little to ensure adequate water flow through any additional devices you may choose to add over and above the simple CHOP 2 configuration.

The beauty of CHOP 2 is that the water is being delivered to the grow beds, fish tank, (and stand alone filter if you like) at pump pressure which makes things work so much better, makes the plumbing easier and makes the water flow control easer and more precise.
Water flows by gravity out of the grow beds to the sump, and out of the FT to the sump.

Some comments have been made about the use of two pumps in a CHOP system, then it is not CHOP anymore. We sometimes use two pumps just to provide redundancy. If one pump dies, then there is another to take over instantly (bit of clever electronics). It is still in essence a one pump system.
In some instances it may be an advantage to run an additional pump from the sump to service and additional filter or a series of raft beds. These can be added or subtracted at will. Very flexible system is CHOP 2

Yes, solids do settle out in the sump but the FT is clean. The grow beds do not catch all of the very fine suspended solids. We have one system running on CHOP 1 (CHIFTPIST if you like). After the water has gone through the grow beds and dropped into the sump/s there is solid matter gathered in the sump/s. Then the water, on it's way back to the FT is split in two. Half goes via a settling trough the other half direct to the FT.

It is amazing how much material is accumulated in the settling trough. We left it accumulate for 12 months just to see what happened. Several Kg of sludge gathered there. Stinking stuff when disturbed and cleaned out and sent off to the compost bin.

In the commercial system we built using CHOP 2 methodology, we have 7 solids collection points which includes the common sump. The sump is the final station in the loops of water movement. A small collection of solids still reach the sump. Very little I have to say but there is still some there.

We have observed that there is better, although only marginal, collection of solids in the grow beds when using a timed system such as 15 minutes on and 45 minutes off. The water movement through the grow beds is much slower and therefore allows more time for the solids to precipitate. Everything is a trade off, because in a timed system the water remains in the FT unfiltered during the 45 minutes that there is no pumping going on, unless your system is big enough to employ a sequencing valve/s to distribute the water to numerous grow beds and therefore keep the water moving through the FT.
Then it is back to small home systems where auto siphons in a CHOP 2 system actually give excellent results without any complications except the need to give the sump a clean every once-in-a-while.

The 7 collection points we designed into the commercial system is not really necessary, we went a bit overboard on that particular job, but it serves to show that if you wanted to collect every tiny bit of suspended solids, you will have a big job on your hands. That many collection points is definately not necessary in a home system.

Collection points...... Just terminology that is better applied to a purely raft system or an aquaculture system. As you are aware I am a great believer in the power of the humble gravel grow bed to collect, process, convert solids into very useful plant and worm food. A very efficient bio filter that we just happen to grow plants in.

Murray Hallam.

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9 Responses to C.H.O.P Operating System. Notes and comments, How does it work?

  1. Dave Spencer says:

    what does chop, tote, chifpist, acronyms stand for?

  2. Sue McLaughlin says:

    C.H.O.P. — Constant Height, One Pump
    tote — IBC container
    CHIFT PIST — Constant height in fish tank, Pump in sump tank

  3. Murray says:

    Thanks for that Sue.

  4. John Blackstone says:

    Good info here, you said “It is amazing how much material is accumulated in the settling trough. ” Is the trough the same as sump here?

  5. Murray says:

    The trough and the sump can be the same. Any container where, as the water travels through allows the solids to settle out. These can be very fine suspended solids that will drop out if given the right conditions.

  6. Troy Martz says:


    I am in the process of researching and designing a system very similar to the CHOP2. It is, in large part, inspired by your hard work, experience, and overall “words of wisdom.” I am eternally grateful for your videos on this subject, and equally inspired by your enthusiasm.

    I would like to present a challenge… Please consider and experiment with a system that can utilize, but is not entirely dependent on electricity, and/or electric parts for operation. (Perhaps this could be the CHOP3?) If the grid goes down, it’s fantastic to have a solar back-up plan, but even solar (with or without a battery bank) is not full-proof.

    Might I suggest that you look at innovative — and sometimes ancient — technologies to compliment your aquaponic system philosophy. Not only would this provide peace-of-mind in the worst case scenarios, but also a clever insurance policy.

    I will be building my aquaponic system with pumps, filters, aeration, and other sub-systems with mechanically-powered devices. Of course these will be powered with electricity, but will also have a machine or man-powered back-up.

    Here are a few examples that — in my opinion — can take aquaponics to the next level:

    – Pump/water lifting device: Consider the “Archimedes Screw,” developed in 300 B.C. (can be powered with a hand crank, belt drive, or gears).

    – Falling water to the fishtank: Consider a waterwheel for additional aeration and power. A waterwheel can also act as a large gear, connected to the Archimedes screw (with a smaller gear), and will pump at least 50-60% of the water from the sump back to the grow beds or cistern… Gravity provides this free energy!)

    – Aeration: Consider a bellows, also powered by gears or belt drive. Of course, air stones or tiny tubes would still be needed, but a bellows system could provide more than enough air pressure for even the largest systems.

    – Regulated Cistern: Consider a very large, raised cistern that, once filled, would take 24 hours to empty. This cistern would supply all the flood and drain cycles for a 24-hour period. In other words, if you fill up the cistern, the rest of the system could — in theory — run perfectly for a given duration. Gravity would again play a large role in this design.

    In summary, a geared-based system could power every device in an aquaponic system with a little ingenuity and careful planning. It’s not only possible, but even feasible to draw less wattage from a gear-based system due to the principle of mechanical advantage (gears, pulleys, inclined planes, levers, etc.).

    I have plans for my system to have 2 levels of fallback:

    1. Primary: Solar-powered engine (with battery bank and grid back-up)
    2. Secondary: A Stirling engine powered by a large Fresnel lens.
    3. A hand crank (in the event it would be needed)

    All three power sources can be interchanged in a relatively quick manner.

    This concept is more of a personal challenge to myself, but I also feel it is a smart decision. Plus, it’ll be fun! I know I will run into issues, will probably go through various prototypes, and most certainly won’t be as cheap or convenient than running out to the nearest aquarium shop.

    I will be more than happy to share my journey with you and your readers if you feel it would entertaining or helpful. Until then, thanks again for the inspiration and knowledge.


  7. Murray says:

    Hi Troy,
    Most, if not all of those options have been discussed in the forum at some time or another, but like anything a revisit with fresh eyes will uncover new angles on old ideas. Look forward to your contributions. Write a blog post and I will put it up….if you like.

  8. Dean says:

    Hi Murray,
    Are you familiar with the hydroponic livestock Fodder systems out on the market currently? They generally use Barley grass and harvest the trays between 7 or 8 days. I’m sure there are some sprouts that would even appeal to the fish in the tanks.
    They can be used to do sprouting for your own use such as alfalfa, broccoli, radish, mung beans and so on. They’re great on sandwiches or in salads.

    I’ve come across several, some the States and some from Down Under. With the CHOP2 method it seems as though there could be a way of growing the same fodder in either a shallow growbed or in a raft setup.

    I’ll be relocating to the Fresno Valley in California within the next year and I thought the fodder trays would make a nice addition to the CHOP2 for feeding livestock such as; rabbits, goats, sheep, chickens, turkeys and 2 0r 3 Jersey milk cows. I’m just not certain what sort of setup might work well. You mentioned experimenting a bit with ideas before giving it the old thumbs up and thought this could arouse your curiosity enough run across your drawing board.

    Just another idea that needs some hashing over and fine tuning to make it a reality and take more power away from Big Agri-Biz controls on food.


  9. Murray says:

    Hi Dean,
    Good to hear from you. It is an excellent concept and I have it on the list of “must-do” things. Trouble is the list is so long……. I cannot see any reason why it will not work and work well. There would be so many uses around the small property, it really must be moved up the list.

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