2mm and 6mm fish food are now in stock as at 1 Jan 2023 December View Fish Food

The Yellow Polka Dot Filter

Filter Yellow dot.The ultimate Aquaponics filter. - Patent pending !!!

The ultimate Aquaponics filter. It has many essential elements in this elaborate design. Look at all the innovative elements, especially the fish centrifuge. That will get the solids out of those little critters whether they like it or not!

There are three clearly defined approaches to what we know as Aquaponics.

1 Aquaculture with some plants hooked onto the end to help with Nitrate control.
2 Hydroponics with a few fish thrown into a tank to reduce the cost of nutrients.
3 Aquaponics as an ECO system, producing wonderful chemical free, clean food in a ecologically sensitive way combining the fish and plants lending both elements equal respect and importance.

Some who approach Aquaponics from the Aquaculture perspective want to get the ultimate filter. They have been led to believe that the more elaborate or the sheer quantity and size of the filter, the better their system will run. That is certainly true if running an Aquaculture system. Aquaculture methodologies are well established.

The idea of adding various gadgets to a system is very appealing to the “tinkerer” that lurks just below the surface in many a bloke. But just how much and what type is needed? Do we really need to filter or not?

There is just no doubt that there needs to be mechanical and biological filtration in any Aquaponics system. The fish in the system produce waste and it has to be dealt with in order for the fish to be happy and healthy.

In a home Aquaponics system the most efficient and convenient filter system is the humble media bed. Various designs have been put forward for a media bed and most of them work rather well, some better than others, but the differences in performance are usually not all that great.

Media BedA row of media filters. Excellent filtration capacity both biological and mechanical.

Media beds, particularly gravel of 20mm (¾”) work exceptionally well. The humble media bed functions as a biological filter and a mechanical filter. It both converts the ammonia produced by the fish waste into useful nitrates which is plant food, and collects the solid material produces by the fish.. Further, in time it also functions extremely well in providing mineralisation of organic material thereby releasing mineral, and myriads of trace elements that one would expect to find in a well found organic garden.

If you run a domestic style AP system with enough grow beds attached, which, in my opinion is how a domestic system should be configured, then you do not need additional mechanical filtration. This is assuming that you are running a balanced system, that is, a system that is not overly loaded with fish and is in balance with the fish and plant occupancy.

More media filters means more vegetables can be grown. More media filters means more fish can be raised.

A really good way to build a very effective media filter is as follows.
Make a solid structure, possibly out of plywood and timber and line it with an appropriate liner. If a poly or fibreglass tank near that size can be found it would be ideal for the purpose.

A suggested good size is 2m long x 1m wide by 0.3 deep. (6’ x 3’x 1’deep)
Fill with gravel of 20mm or 3/4" (make sure it does not contain limestone.)

Gravel FilterThis gravel filter is approx two square metres (2 square yards) in size. This one is getting new gravel after six years in service cleaning the fish water, processing ammonia and growing a huge bounty of vegetables, particularly fruiting vegetables such as tomatoes and the like.

Pass the water of your system directly through this wonderful filter. Various methods can be employed to do this; a constant flow or flood and drain. Various plumbing and pumping regimes can be employed to regulate and distribute the water.
I have been using this style of filter for many years. They work exceptionally well, requiring little cleaning and minimal maintenance.

I have also discovered that worms will take up residence in this filter system..... Wonderful stuff. We all know what worms do for any garden. They are particularly important in an Aquaponics garden, processing solid organic material and releasing a myriad of minerals, and micro nutrients. The worms also play a vital role in the maintenance of the filter by reducing the volume of collected solids by up to 80%. The plants do really well, because, amongst other things, the action of the worms releases and makes available nutrients for these plants.

Much to my utter amazement I have found that , by growing plants in the top of this filter (I grow veggie types of plants) the efficiency of the filter is further enhanced. By growing plants in the filter I found that the Nitrates that are naturally produced by this very effective bio and mechanical filter, are used up by the plants. This wonderful little benefit means that I do not need to discard water on a regular basis to keep Nitrates under control. (Discarding water to lower Nitrate levels is common practice in aquaculture systems.)

I know this all sounds very unscientific.....but hey....it works and works astonishingly well.!

I have been running such systems now for more than 6 years, sold and installed hundreds of kits across Australia and also into the USA, NZ and China. My kits and that of the other only credible kit manufacturer in Australia, are highly successful. Clients enjoy a very high degree of satisfaction and enjoyment. Further to that there are literally tens of thousands of DIY system builds around the world using the humble media bed filter with excellent results. As far as we are able to tell we believe there are over one thousand Toteponics systems built from my plans utilising CHOP 2 methodology.
I am totally confident in what I say based on solid verifiable experience.

There are those who promote adding mechanical filters way beyond the humble media bed. These folk are actually trying to push fish production way beyond what a home based Aquaponics system should. This is actually home Aquaculture.

If you want to go outside that balance and push for more fish production and actually turn your AP system into a half baked Aquaculture system, then you need to start adding aquaculture like equipment such as moving bed filters, swirl filters and so on.

By going in the aquaculture direction, the beauty of the simplicity of a well balanced Aquaponics system is lost and it becomes ever more complicated to maintain and run.
This may be the deliberate choice of some operators of home systems.
If you want to add filters, then go for it....have fun....knock yourself out, add a couple, or three.

Some people that go on and on about filtration, are heavily influenced by Aquaculture people and have a strong aquaculture bent. They have lost sight of the beautiful thing about home AP, and that is ...it is an ECO system. It is NOT Aquaculture and it is NOT Hydroponics. It is Aquaponics.

An AP system is an ECO system so therefore must be in a balanced state. This should never be forgotten. Aquaponics as an ECO system is a system for this time in history. More and more folk are realising the importance of growing food using all the natural processes possible. There is increasing rejection of systems that rely on chemicals or push things way beyond natural limits. A balanced ECO system such as Aquaponics allows for the raising of food fish and vegetables in a symbiotic relationship.

The great majority of home system owners, especially those that have purchased a ready made premium kit are not interested in additional complications in running a system. They are very attracted to the beauty of the ECO system. It fits well into their idea/desire to move towards a greener more sustainable lifestyle.

There is an element amongst the AP - DIY world that enjoy tinkering. For those people, build yourself at least one of every kind of filter you can think of and ...enjoy. Tinker away till your heart is contented.

Why not build a replica of the Yellow Polka Dot Filter and attach that to your system?

The Yellow Polka Dot FilterThe Yellow Polka Dot Filter. It just might be the ultimate filter for the home aquaculture system. Those who feel they need additional mechanical filtration, want to get into home aquaculture, and you just love to tinker!

Please take note, if we were to build a full blown Commercial system we would approach the design with a different set of parameters to produce a commercially viable system while still maintaining the beauty of an Aquaponics ECO system.

Murray Hallam of Practical Aquaponics is available world wide to consult on design and commissioning of commercial scale Aquaponics systems that are efficient in design and maintain the working principle of an ECO system.

PS.... Come to my Commercial and Small Farm Training at Pescadero California December 2 to 6 ....2012. See here for more info about all my training classes in Australia and the USA.

Posted By Murray Hallam on 16th October 2012

Updated : 28th June 2019 | Words : 1518 | Views : 11323 | Comments : 22

RSS Twitter Facebook



Ive just harvested some 30 month old silver perch and they taste like barramundi a bit muddy I suppose but very chewy, smoked of course. I'm looking forward to the next feed as in three weeks I have to move all of my system to my new premises

Posted By martin on Tuesday 23rd October 2012 @ 09:07:33


Hi Martin,I eat mine no later than about 18 months old. Smoking if overdone can make fish a little "chewy" Hope you have better luck with the next batch. Jade Perch are more oily and therefore smoke much better. Smoking any type of meat product tends to dry it out.

Posted By Murray on Tuesday 23rd October 2012 @ 09:07:33


Thanks VERY much for this: I've been experimenting with gravel beds, wondering which is the best way to go.

Posted By jujigatame (Walks-In-Storms) on Thursday 18th October 2012 @ 12:57:22


Hi Muray
Thanks for your comments. I am at Coffs Chrisitan Community (I haven't worked at Jetty). My system has been in operation since 2007. We are also working on some projects in Bali where we support some orphanages and partner with another school in Denpasar.

Posted By Garry Graham on Thursday 18th October 2012 @ 00:57:55


Sorry, wrong Garry. Great thing to do, and all the best with the overseas institutions.

Posted By Murray on Thursday 18th October 2012 @ 00:57:55


One of the issues that I have experienced with growing plants in a gravel media bed is that as organic matter accumulates, plant performance decreases. This issue has been addressed by the University of Virgin Islands some years ago, and is one reason why they use only floating raft culture. When organic matter accumulates, especially from root hair debris, a bacterial film forms on the roots (they lose their clean white colour and look a dirty brown colour)and inhibits nutrient uptake. As a result the plants struggle to thrive.

The only solution is to remove the gravel and wash out the organic matter. When there are 8 grow beds, as I have, it is quite a job. I now clean beds on a progressive rotation over two years. I have also converted a couple of beds to the floating raft system, simply to reduce the back-breaking work load! My system is at my school (I am a teacher), and my Marine Studies students provide some valuable labour to assist with the cleaning schedule - purely for educational purposes, of course!

I currently use a simple swirl clarifier to reduce solids, but I am designing an equally simple screen filter to add to my system design. However, it needs to be remembered that the solids are loaded with nutrients, and so we should aim to balance the need for clarified water without removing an important nutrient source too quickly.

Posted By Garry Graham on Wednesday 17th October 2012 @ 21:33:05


Excellent comment Garry,
Careful reading of all the UVI material reveals some very interesting reasons why they have a bent towards raft culture. Using media beds as filters works excellently well provided sensible management is applied as you have alluded to in your comment. Your use of the clarifier is also wise to pick up the initial bulk solids. Reprocessing these valuable organic assets is imperative if a nutrient balance is to be maintained. Are you still at the "Jetty" school?

Posted By Murray on Wednesday 17th October 2012 @ 21:33:05


I have added radial filters to my three AP systems with great results. the filtering of solids before they go into the gravel beds is good practice and it means less buildup of sludge in the growbeds to be cleaned out later. nothing wrong with extra filtration but of course no need to go overboard with it if you just have a small basic backyard system.

Posted By Dave O ponic on Wednesday 17th October 2012 @ 05:17:53


So true Dave, some extra filtering is OK if one really feels the need, or there is a need because of heavy stocking for the size of the system. It needs to be recognised that 1, Aquaponics is an ECO system, hence the need for balance between the fish and the plants, and 2, Media beds are a great filter in their own right, efficient and a long time between cleaning maintenance.

Posted By Murray on Wednesday 17th October 2012 @ 05:17:53


Muddy taste can also come from algae eaten by fish, especially Tilapia. Try withholding feed for several days before harvesting your fish. Also keep the walls and floor of your tank clean so there is not so much algae in their diet.

Posted By Dave O ponic on Wednesday 17th October 2012 @ 05:14:45


Personally, I have never encountered a "muddy "taste in any fish I have grown.

Posted By Murray on Wednesday 17th October 2012 @ 05:14:45


Have been into aquaponics for about 3 years. The fish tast very "muddy" .Any suggestions?

Posted By Neil Cooper on Tuesday 16th October 2012 @ 20:53:56


Hi Neil,
"Muddy "taste comes from poor water conditions, typically over feeding and less than ideal filtering, or more likely in a home Aquaponics system too many Nitrates in the system which is the final outcome of the first things I have mentioned. My guess is that you do not have enough plants in the system to take care of the Nitrates being produced.
Solution.....plant more plants into more media beds.....but in the short term. Condition the fish befoore eating by removing them into a separate tank with a good filter on it....lightly salted and no feeding for a minimum of three days before processing onto the BBQ. How much salt used depends on the species of fish. Most Australian native fish are very salt tolerant. I am sure that will help.

Posted By Murray on Tuesday 16th October 2012 @ 20:53:56


Wow you really let them have it, you
can't teach someone who knows it all anything. Keep up the good work I love what you are doing. I am going to try to come see you in December. J Mark Bogart Valley Aquaponics.

Posted By Mark Bogart on Tuesday 16th October 2012 @ 19:15:51


Hi Mark,
Looking forward to seeing you in Redwood Country.

Posted By Murray on Tuesday 16th October 2012 @ 19:15:51


Ah, but where are the small plane (for using the propeller to cool the system), and the Volkswagon (I use the engine to supply at the power required)"

Oh, yes, and the cat. I find that stationing a cat on a walkway over the fish tank keep the fish agitated - scares the poop out of them, you know.....

Posted By jujigatame (Walks-In-Storms, actually). on Tuesday 16th October 2012 @ 12:30:14


Yeah WIS, there was a lot more I could have done with the drawing....lot of fun.

Posted By Murray on Tuesday 16th October 2012 @ 12:30:14


Yup it's the simple and workable system that is best...the less moving parts the less problems...however my father an ex-battleship engineering officer tend to look at it in a complicated technical manner...don't know how many times I've quarreled when we were designing the filters...*sigh*...we're just trying to get some tomatoes and cucumbers to sprout...not managing a water purifier plant...

Posted By Omar on Tuesday 16th October 2012 @ 10:25:40


Hi Omar, Some people just like to tinker and if that is where they get their joy, then may they long tinker. You are so right, this is one discipline where "less is more" really is true.

Posted By Murray on Tuesday 16th October 2012 @ 10:25:40


EC Measurements in an Aquaponics System


Posted By Practical Aquaponics on 2nd May 2018

Views : 67362 | Comments : 0

The Most Compelling Reason

Food Purity Food purity is one of the main reasons a lot of people get into aquaponics. Every time . . .

Posted By Murray Hallam on 30th December 2017

Views : 63769 | Comments : 0

Aquaponics Book of Plans. Tried and Proven Plans to Build

Do you want to build your own home Aquaponics system but not too sure where to start? What materials . . .

Posted By Murray Hallam on 31st December 2014

Views : 61899 | Comments : 0

Share with Us


Additional Information


Murray Hallam is probably the best-known face in the world-wide Aquaponics movement. Murray is by nature an innovator and in his Research & Development facility has perfected many new methodologies for commercial farm Aquaponic systems.


Learn Aquaponics

At Practical Aquaponics, we have a range of information suitable for the novice to the expert. Browse our blog, register for our Aquaponics Courses, Workshops and Seminars or buy kits, books, DVDs and many other aquaponics necessities in our shop.


Aquaponics Kits & DIY

Proven and tested, there are hundreds of our kits in operation in every state of Australia and we have exported our kits to the USA, Hong Kong, New Zealand and Nassau. The wonderful thing about Aquaponics is that almost anyone can participate and get to grow some clean, healthy vegetables and fish.



Everything you could possibly need to set up an Aquaponics farm or home system is found in our online store. Whether you are looking to do Aquaponics in Brisbane, Perth, or anywhere in between, we’ve got you covered with the best range of products Australia-wide.


Featured Products

Indy 23 System - Plans And Building Instructions

Indy 23 System - Plans And Building Instructions

Feed Four People Year-round With The Indy 23 Aquaponic System! Build Your Own, Using This Step-by-step Instruction Set. ...

from $395.00 buy online

Consultation With Murray Hallam

Consultation With Murray Hallam

If You're Working On An Aquaponics Project (or Thinking Of It), A One-hour Consultation With Murray Hallam Can Help Clear Up Some Of The Questions You ...

from $170.00 buy online

Autosiphon (bell Siphon) Kit

Autosiphon (bell Siphon) Kit

The King Of Media Bed Water-outlet Controllers! The Auto Siphon (bell Siphon) Controls The Flood-and-drain Cycle Of Your Media Beds. An Easy, Troubl ...

from $89.90 buy online

Call our team today on 07 4156 5368

For all things Aquaponics ... Practical Aquaponics is your number #1 choice for products and information. Give us a call or drop us an email about your farm project today.