Aquaponics CHOP Mark 2 Operating System.

CHOP or Constant Height One Pump has been adapted by Aquaponics enthusiasts around the world now for the last few years since we coined the term.  The other variant Chift Pist runs in a similar way.  I noticed a problem with water levels whilst working on a small commercial CHOP system we were commissioning just over a year ago.  We needed to refine the process for our client,  so we came up with a solution that we’ve been trialling now for over a year.

CHOP Mark 2

It runs so beautifully. I’m very excited by it.

I am so certain this is a better way to run your aquaponics system that we have adopted CHOP2 into all our new larger Aquaponics kits that we design and build.

So what is CHOP Mark2 and why should you consider using it?

Operating the old CHOP method water is pumped up from the sump to the fish tank and from the fish tank runs back to the grow bed and sump by gravity. This system works very well but it requires that the grow beds be perfectly level to function properly. With CHOP Mark2 there are a number of advantages you can study if you watch and play the accompanying animation.

See Animation HERE

With CHOP2 you will notice that the pump sends the water to the grow bed as well as the main fish tank simultaneously. The water from the fish tank and grow beds runs back to the central sump.

It’s kind of like a double loop water flow with the sump as the central mixing point. It works extremely well.

So what are the advantages of modifying your system to CHOP Mark2?

The main point is that grow beds do not need to be perfectly level to function properly.  A crucial point if you are running a number of them on uneven ground and have encountered problems with your auto siphons. Because each grow bed has an independent ball valve, the water flow can be regulated with greater control than gravity fed flow under the old CHOP system.
Recently we commissioned an 18 bed system utilising two of our large commercial fish tanks.  To facilitate good water flow we used CHOP Mark2 together with sequencing valves.

Because each Fish Tank also now has its own ball valve it means water flow to the fish tank/s can now also be regulated as well.

If you need to harvest your fish and control the water depth or do any maintenance at all, you now have complete control to stop water flowing to your main fish tank or even drain it,  but not stop the flow to your other grow beds.

More control for the aquaponics enthusiast also means more control over winter temperatures as the mercury plummets.

In colder climes operators can turn off their grow beds at night but still have their main fish tank running as normal.  This is a great boost for owners who complained that their grow beds were acting as a heat sink at night, plunging their water temperature down a number of degrees.

A side benefit for users who will modify their system to CHOP Mark2 is that should they decide to change their system from a gravel based media to floating raft, CHOP Mark2 will accommodate their design shift.

If a combination media and raft system were to be built,  Swirl filters or regular filters can be fitted easily into the fish tank to raft section, then we can allow the rafts to drain back to the sump.

An elegant solution.

But what are the disadvantages of running this system?

The critics will say that the sump pumps half the water back to the fish tank. Surely this can’t be good for the fish, as solids are returned back to the main tank?

Logically this may seem to be the case, but over a year of trialling this system with hundreds of fish we have discovered that the sump itself acts as a settling tank for solids, something that we didn't expect to see and something that has never happened under the old CHOP system.

You will need to clean your sump occasionally as the solids will be noticeable around the sides of the sump.  This is a good thing and it is not hard to do.

What about fish nutrients?  Aren’t you halving the number of fish nutrients by returning the flow back to the main fish tank?

Some may think that the nutrients from the fish tank will be diluted as the sump water is pumped partly back to the fish tank and partly to the grow beds.  In just over 12 months of running we see no reduction in nutrient to the grow beds.
Conversely,  some may think that the nutrient level may be too high and perhaps there will not be enough filtration or bacterial action because some of the water that has just arrived in the sump from the fish tank will be returned directly back to the fish tank.

We initially felt some of these fears ourselves, but with 12 solid months of field trials behind we see the systems running exceptionally well.

We see CHOP2 as a definite improvement for the Aquaponics community around the world.  Come back in 12 months time as see how many users have modified their system to CHOP Mark2.
People always vote with their feet. They know when they’re onto a good thing.

The next generation of CHOP.   CHOP Mark2

1  Grow beds do not have to be exactly level with each other as they do for CHOP mark 1
2  Flow to the grow beds can more easily be regulated than with a gravity flow.
3  Fish tank can easily be isolated if required for whatever reason.  We regularly switch off the fish tank to pump it down to do a fish count or capture and the grow beds are still left running.
4  Grow beds can easily be isolated if winter night time shut down of the flow to the grow beds is required while fish tank still enjoys excellent water exchange.
5  If a combination media and raft system were to be built, swirl filters or regular filters can be fitted easily into the fish tank to raft section then rafts drain back to the sump.

Happy Aquaponics

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37 Responses to Aquaponics CHOP Mark 2 Operating System.

  1. Congratulations Murray on a substantial improvement to what was already an elegant design! You are a true innovator and substantial contributor to aquaponics around the world.

    There is one thing I don’t understand in the diagram. What function does the long vertical pipe inside the fish tank serve? Isn’t the tank water just going to overflow horizontally out of that pipe at the top of the tank?

    thanks again for all you do!

  2. Ernie Yribe says:

    It appears you may be missing the extra water source for the sump tank when it begins to lose water. It was mentioned in our workshop in Oceanside, California that you add a float valve with a water source to prevent the sump tank from running out of water. Are you attaching this float valve to a gravel fed barrel or reservoir or to a house fauset? If so (from a house fauset), it may also appear that a chlorine filter may be in order. How are you adding this in your diagram? Or can you maybe describe how you do this? Many thanks for all your updates. I am getting ready to set up a CHOP system and with this added information, I will now look to setting up a CHOP2 system.

  3. Admin says:

    Hi Ernie,
    The float valve attached to a water source is definitely part of the system. It is located in the sump. Re the chlorine, we find that in actual practice it does not matter, the float valve lets in so little new water each time it opens that it has no measurable effect. But a chlorine filter could be added if so desired.
    I will post a more detailed diagram very soon to show each little detail.

  4. Admin says:

    Hi Sylvia, That vertical up stand makes the exiting water come from the bottom of the fish tank. That way we make sure the water in the fish tank is exchanged and fish wastes picked up from the bottom of the tank. To assist in picking up the solid fish wastes I use a stiff broom with a long handle to scrub the bottom of the fish tank once every couple of weeks.

  5. Great stuff , its all about improvements and quality ,so congratulations


  6. David Armstrong says:

    Does this design require a larger pump as you are now pumping in 2 directions.?

    Also, why not return the fish tank water via the grow beds. This would ensure that all the fish waste is being “processed” rather than collecting in the sump and even if the gravity flow to the grow beds is irregular (because of height differences) this shouldnt matter because of the direct pumping from the sump

  7. Admin says:

    Hi David, You could return the water back via the beds, but then it would require a different plumbing set up that would bring you right back to CHOP Mark 1…which worked fine.
    We know there are advantages in CHOP Mark 2 which are summarised at the bottom of the blog. In practice, all the fish waste is taken care of in CHOP Mark 2.

  8. november9er says:

    i m exhited about this new improvement on CHOP. sure will keep me busy this Mel.Cup weekend. these kinda innovations keeps the obsession more n more … positive. thanxz heaps.

  9. november9er says:

    was pondering over lunch at the illustration and a thought occur. modify CHOP Mk1 by installing a Y connector on the overflow to GB and a T connector on the sump pump. pump would send h2o to FT and assist overflow to GB thru the Y, this should maintain the cleanliness of the ST. no backflow should occur at the Y connection. watcha recon M ?

  10. Admin says:

    Hi November,
    I think I can follow your idea. You will be depending on the venturi effect to aerate the water on its way to the grow beds ?????
    It could work. Never knock a new idea till you have tried it I always reckon. Later I will draw a mud map and see if I can work out what it is you are thinking. Perhaps you could send me a mud map and we can compare notes.
    email [email protected]

  11. MalcolmC says:

    Well done Murray.

    I’m currently sitting in Wilpena Pound (actually Hawker) so will have to wait until mid December to trial CHOP2. ;-)

  12. John B says:

    Thanks Murray, I’m just about to do the pipe work for my first CHOP system, . I’m using a 1000 Lt tank with 3 bath tubs for my grow beds and a large bath tub for the sump. After seeing your Chop2 set up I think I’m sold and I’ll be going down that path. I would appreciate your detailed plan and advise on pump type and size so I can kick the system off soon. Might have to come for a drive to pick some bits up!

  13. Admin says:

    Hi John,
    It will be a few weeks before we have a detailed set of plans. We will also have a pump and pipe kit available.

  14. Leevi Graham says:

    Timely post Murray.

    Am I right in thinking that another benefit of this system is the the grow beds can be higher than the tank now they are not gravity fed?

    Also with Chop Mk2 Can the sump be smaller? What ratio of sump to growbeds would you recommend.

  15. Admin says:

    Hi Leevi,
    The sump needs to be big enough to take all the water from the grow beds should the all decide to dump together. Rare, but it does happen. If you have an elevated site for the grow beds then you may be able to auto siphon back into the fish tank and do away with the sump altogether. Some have very steep sites, this arrangement is then very suitable for their purpose.

  16. DaveOponic says:

    Interesting design Murray, but why not put the pump in the bottom of the fish tank? This will remove all of the solid waste. (You won’t need that broom.) I have done this as I don’t have a fish tank that is higher than my growbeds, therefore I can’t gravity feed (as in CHOP 1) In your new CHOP2 you pump to growbeds. I pump to elevated sump/swirl filter, then gravity feed to GB’s and gravity flow back to FT. Since you are suggesting the use of two pumps, why not put one in the FT and one in the sump? Also connect FT and sump at low height with a pipe to maintain water level. Cheers, Dave.

  17. Admin says:

    Hi Dave, Thanks for your input.
    I should outline that all our Premium kits are designed to deliver a good result to the client who wants to have a system that works well, delivering clean chemical free food to their table. The kit has to be functional, easy to operate, and be tidy…look good in their back yard.

    There is an even greater number of folk who just cannot afford one of our Premium kits, but are keen to build one themselves by following some simple easy to follow instructions that will produce a very happy result. Our home kits designs suggestions such as CHOP are for these folk.
    There is also the education sector. Schools require a system that will work, work to an acceptable level. It simple to operate, will be installed/built on a level site requiring a minimum of daily maintenance.

    Our kit suggestions are not for the tinkerers who possibly get more fun out of the tinkering than from eating the veggies and fish. They will go on adding bits, pink pipe, yellow pipe and whatever they think or decide to give a try.

    You asked, “why not put the pump in the bottom of the fish tank?”
    Well, we do just that for all of our smaller Balcony kits, and it works just fine. We use a low profile tank for that style of system and the grow beds are higher so they auto siphon back down into the fish tank. I guess you could say that it is both fish tank and sump. Even running such easy , low pooping fish such as Jade Perch the broom trick is most useful, once in a while, not just for any poop or uneaten fish food, but to give the sides and bottom of the tank a scrub to remove some of the bio film. It keeps things looking nice.
    Your pump may remove all the solid waste from your particular set up. I am sure it does if you say so. In our Balcony kit range the pump removes 99% of the waste and a little stiff brooming does the rest as described.

    You pump to an elevated swirl filter/header tank. Excellent idea. We built a very large domestic job that had close to 100 metres of NFT and two of our 5 metre troughs as floating raft. We employed that very technique. We hoisted one of our very fine, good looking FG swirl filters atop one of our very fine good looking round 1000 litre tanks which became water storage. They fit perfectly because we made them that way. You can do that with FG. The tank was strong enough to hold a swirl filter that weighed close to 900 kg when operational. Together with the water storage in the tank below the combined weight was very close to two tonne.
    Can you imagine the legal implications if we were to start recommending people hoist heavy objects up into the air at home. Most would be built on inadequate bases and a disaster is in the making. If we recommend it, we cop the blame, if it goes bad.
    It is a great idea and works well, but not very good for the Premium Kit buyer or minimalist home kit builder. It falls into the category of “too hard”. Fine for the tinkerer.
    You ask “Since you are suggesting the use of two pumps, why not put one in the FT and one in the sump?” Yes, one could do that, but we left that design behind four years ago. The suggestion for two pumps as a Mod in CHOP Mark2 is to provide redundancy. The primary purpose is a safety issue for the fish. The home kit builder we are trying to help will not check his system every day so, It is a fish safety issue. The home owner or village chief wants to harvest the fish at the end of the period.

    You further suggest : “ Also connect FT and sump at low height with a pipe to maintain water level.” That would require the fish tank and the sump to be the same height at the top. That would mean , in reality a second fish tank, or a smaller sump elevated on a stand of some sort or dig the fish tank into the ground, or a sloping site would help as well. Not a practical option for our intended end users.

    Dave, I really appreciate your feedback, because it is feedback, not a diatribe of hate. I just wish people would get a grip on where we are coming from and what we are doing.

    Our CHOP system instructions will not make us much, if any money at all. It is designed to be a simple to construct system that actually does work that anyone with some tools and a minimum of skills can accomplish. It will be built on a flat piece of ground and will not endanger anyone. We are providing a community service. It might sound “corny” or a bit “fruit cake”, but I really believe that AP is the food production system of the future. It is not the only way, but it is a darn good one. Simple CHOP systems can be built in underdeveloped countries as well as in our back yards with a very high degree of success.

    I should also point out in the strongest possible way. WE HAVE BEEN RUNNING CHOP 2 FOR OVER 12 MONTHS and IT ACTUALLY WORKS VERY WELL. I would not recommend it if it did not work and I had not already built and run such a system . Yes there are at least five dozen things you could do to change it, maybe six dozen if we were to run a competition of discovery.
    There are many methods one could employ to remove that last five percent of fish waste, make the water move in ever decreasing circles, or deliver a treat to the fish every time they perform a trick but it is like “spending fifty dollars on a five dollar problem”.

    We have 9 possible Mods for the CHOP Mark 2 system that we will be putting out over the next few weeks. (it might be 10 or 15 by the time we are half way there) Simple things the average backyard Joe, or the village mechanic can accomplish.
    Am I making a fortune out of this…..I think not.

    Just watch, many thousands of these will be built and work very well for everyone who follows the simple instructions.
    Just watch, the flow of criticism from certain quarters will continue. (That would happen if I were to recommend porridge for breakfast)

    We actually benefit from customer feedback. We have thousands of actual clients, and and that is ever increasing. The feedback we get form our clients in invaluable. It is these people we are aiming to please. We don’t get it right every single time. But every time there is something we can improve upon we do so immediately.

    Sorry about the long winded reply. I have assumed that you are really interested to understand what it is we are trying to accomplish, and what it will accomplish.

    Thanks Dave.
    Have a nice day and above all Happy Aquaponics
    Practical Aquaponics.

  18. Wendy says:

    Hi Murray
    Really loving your stuff – I am new to this & still at the planning stage – I’m having a little trouble understanding the pipe in the fishtank. I understand that it will drain from the bottom of the tank to remove solids etc. but it seems to me that it is actually siphoning & relies heavily on the water pumped from the sump to maintain water levels in the fish tank. What happens if the pump fails – does the water get siphoned out, overflowing the sump & leaving the fish stranded ? Or have I misunderstood.

  19. Admin says:

    Hi Wendy,
    The up stand coming up out of the fish tank from the bottom has a 1/4″ (6mm) hole drilled in the very top of the bend to stop it siphoning. The drawing at the head of this article shows another arrangement where the up stand pipe is actually extended well above the waterline and is left open ended to allow air into the pipe and thereby preventing a siphon. The water exits via the middle of a “T” fitting.
    The water coming out is, and must be equal to the amount going in.
    If the pump stops for any reason then the water flow stops, the tank remains full and all is well.
    Naturally the water flow needs to be restored ASAP for the health of the system.
    We have a backup switch that activates a 12 volt battery backup pump that takes care of short term outages.

  20. Andrew says:

    Hi Murray,

    Interesting development – just to be clear, this will require a larger pump than a basic CHOP won’t it?



  21. Murray says:

    Not really, the same amount of water is being moved, we are just moving it in different directions. In a basic CHOP all the water is sent through the grow beds and any excess water that the pump can move is bypassed back to the sump. All that we are doing is sending that excess water through the fish tank. A bigger pump is fine to send even more water through the fish tank and back down to the sump. The amount of water that will go through the grow beds is limited by the ability of the auto siphons to process, so however much will go through the grow beds, will go through the grow beds. All the rest can cycle through the fish tank.

  22. Andrew says:

    Thanks Murray, In my current CHOP system I sized the pump to give a full change of water in the fish-tank once an hour – how would I size it for CHOP2?

    e.g. If I have a 1000l fish tank, and 1000l of growbeds (assume the growbeds need 400l of water) in my CHOP system I would use a 1000 lph pump which would flush the fishtank and overflow into the growbeds.
    In my CHOP2 I’d presumably still want 1000lph for the fishtank, plus now 400lph for the growbeds?

    Sorry for the detail questions. but I think it looks like such a good idea I’m working out how to implement it!



  23. Murray says:

    That will work really well Andrew

  24. Gary says:

    I’m trying to get the most sustainable ecosystem I can with as little outside support as possible. Is it possible to grow duckweed in the sump tank? Perhaps a better question is, how can I fit a duckweed area into the system. Or are there better ways to feed the fish?

  25. Murray says:

    You will not be able to feed your fish on duckweed alone and get good growth. Duckweed is an excellent food for the fish, but you will need some others as well to make sure the fish get everything they need in their diet.
    You can grow it in your sump provided the sump get enough direct sunlight.
    It is relatively easy to set up a duckweed growing tray attached to your main system

  26. Yvonne says:

    Hi Murray, We are currently putting together our DIY system of 1000l FT / 100ol approx grow beds. A quick question about the auto siphon. Does it need to drain directly back to the sump to work properly? One of the grow beds is not directly over / next to the sump. Can we plumb the auto siphon drainage line to ground level and back up to enter the sump – to make it a neater job, and the siphon still work?
    Thanks for your help, Yvonne

  27. Murray says:

    Usually no…sorry. It will most likely not work for you.

  28. Zac Wentzell says:

    Referring to the CHOP 1 system:
    “This system works very well but it requires that the grow beds be perfectly level to function properly.”

    Murray, could you please explain why that is?

  29. Murray says:

    Hi Zac,
    The inlets to the beds must be level with each other in order for there to be equal gravity flow to each bed. If one bed is a few mm higher than its brother beds it will get much less water or none depending on the height difference.
    This can be dealt with by adding some sort of tap to the inlets to allow fine tuning of the flow to each bed. This still has limitations on regulating the flow. In CHOP 2 the water is pumped to the beds and is much more easily adjusted to even out the water delivery.

  30. Charles Brown says:

    Just set up a micro chop2 system in my living room using my 75 gallon(283L) aquarium that has been operating on it’s own filter system (Marineland 400gph Bio filter) for 6mos.
    I’ve plumbed in (2) 41L grow beds and a 68L sump w 250gph pump (up grading to bigger pump tomorrow..). No vegetation in beds yet just cycling for a week. Question:
    Will the aquarium filter have a neg. effect on the level of nutrients to grow beds?
    Thx for the pioneering work on this system. Love the constant height of my aquarium. My friends who introduced me to aquaponics were amazed to see my set up using Chop2, they had no idea of it.
    Thanks to Meg Stout who’s blog really help me understand your system.
    Aquarium enthusiast for over 30 yrs, new to gardening!

  31. Murray says:

    Good work Charles,
    Personally I prefer to leave the solids in the system…all that fish poo with all that nutrient. Obviously you need enough grow bed volume to be the filter for the fish. The grow beds are the filter and happily we grow plants in the filter. If you lean more toward having an aquaculture system with a few plants, then, yes you need additional filtration. It is all about balance. Aquaponics is an ECO system, which aquaculture or hydroponics are not.

  32. Anton van der Merwe says:

    Hi Harry,
    I bought you DVD set a couple of months ago and have viewed at at least 20 times!! Great. I learn something new every time!
    I will start a 5000L CHOP Mark 2 system in a couple of months.
    Could you please tell me where I can get a download-able design drawing for this system.
    Love your work and thanks for the service you provide

  33. Murray says:

    Hi Anton,
    The PDF file containing the build instructions and component list, pump details etc is on the Aquaponics DIY dvd. It can also be downloaded from the SILVER members area on this blog.
    I hope this helps.

  34. Charles Brown says:

    Gotcha Murray.
    Also error on size of 2 grow beds they’re 16.75 gallons(63.40L) by sterilite.
    Since my post, “ICH” _ _ _ _!, now what do I do? After plumbing and tuning ebb n flow, late nights clocking and insuring siphon breaks….THIS. And sure it came from a 42nd birthday gift from my daughter, a new African chiclid. No Problem Practical Aquaponics and forum members to the rescue. Thx Again. Now I can scream a different four letter word SALT! Will continue in appropriate channel

  35. Murray says:

    Good Charles, I am glad it is going OK for you.

  36. Ricky says:

    Is it possible to design a system with only one tank. Plants floating on top, fishes swimming in the middle and bio-degrading in a substrate at the bottom? Would only need air pump to aerate and circulate the water in such a system. Would this work? Anybody tried? Comments please.

  37. Murray says:

    Yes, it has been done many times. Ned to use a fish that will not eat the roots of the plants.

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