Solids Removal in Aquaponics

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Solids removal is an important part of any aquaponic system.

raft aquaponics

Raft systems are not only very space inefficient, they also require a lot of mechanical solids filtration to keep them functioning properly.

In raft systems this becomes expensive- you have to use some type of filtration to remove solids so that your raft beds don’t accumulate waste, your DO doesn’t crash, and your plant roots stay healthy.

Media based techniques on the other hand, use the media bed to remove solids.

Here at Bright Agrotech, we use our ZipGrow towers as mechanical filtration, sending almost all of our solids into the tops of our towers.

Redworms and bacteria take it from there, breaking up the solids as quickly as they accumulate.

Media-Based Aquaponics Systems

If you’re already using a media based system, then solids probably won’t be an issue for you, unless your stocking densities are too high, or your medium is too fine.

If your stocking densities are too high, you’ll be producing more waste than your media bed can break down.

solids removal in zipgrow towers

ZipGrow towers in a 55 gal system (Build your own here:

If the medium itself is too fine, then the waste can impede the flow of water through your bed, clogging things up and causing the water to go anerobic.

This happens because the decaying waste consumes all of the dissolved oxygen.  This is one reason why it’s important to use larger media sizes (not pea gravel or sand!).

Our medium is rather coarse (93% void space), so it allows water to travel freely through the material, even when there are lots of solids present.

 Read more on Biological Surface Area in Aquaponics Here. 

Raft Systems in Aquaponics

If you have a raft system, then you’d better invest in solids removal equipment.  This reduces the overall nutrition in your system, but if you have proper mineralization tanks you can still maintain relatively high nutrient levels.

The Cost of Filtration

Solids filtration can be expensive- it’s one reason why we really like to use our trusty ZipGrows.

There are lots of great resources out there on how to build your own equipment so that you can save some money.

There are lots of great techniques- you’ll just have to do your research!



  1. Hi Nate,
    Thanks a lot for another really interesting post!
    If I understand good, a good media will act as a filter for the fine waste and the fine particles are mineralized directly into the towers. The bigger, heavier particles are trapped in some settling tanks you say. Is it something relatively cheap like swirl filters or radial filters ?

    Then, where in the circuit should those settling tanks be fitted ? You describe a plumbing in several loops being ideal (see video on one-pump systems here : Do those settling tanks have to be in the same loop as the fish tanks ? Or do they constantly filter a part of the sump water ?

    I will be following your other videos, thanks again for inspiring us!

    • Swirl filters will work. We recommend filtration being downstream from fish production – typically between the fish and the sump tank. Hope that helps!

  2. The caption under the first picture reads;

    Raft systems are not only “very space efficient”, they also require a lot of mechanical solids filtration to keep them functioning properly.

    Did you mean space efficient for space inefficient? I thought i had previous read in the resources you provide that rafts were not efficient in there use of available space.

    Cheers guys.


    • Good catch, Danny! On a space-efficiency scale, you are correct, rafts are very inefficient.

  3. Just wanted to say that I enjoy the videos and blogs you guys post for our benefit. I’ve been working on a small scale system and experimenting quite a bit and I have to say also that you have helped me fore see several mishaps! Keep up the good work, it is much appreciated and enjoyed!

    • You’re quite welcome, Ryan! Glad this blog and our videos have proven useful to you. Hopefully you’ll help us spread the word.

  4. If you have media beds before rafts will that solve your solids problem?

    • They can certainly help, but we wouldn’t rely on them if you’re planning to do raft production. Raft production is pretty difficult to do without some fairly expensive solids removal equipment.

      • That’s not true, There are some very good DIY options that exist. From my expereince you would need a really good solid removal system to not clog your drippers.

        • Great point, John. There are many DIY options out there. Finding the right one for your system is the key. That, and having the time, energy and know-how to make it happen. Very possible!

    • Hey Niklas, the redworms just stay inside the media for the next planting. They love it.

  5. What do you do with your big solid waste that settles in your settlement chambers??

    Do you mineralize the waste in tanks, separated from the main system, so to slowly add this nutrient rich water, after waste has been mineralized, from these tanks into the grow beds?? This is what I have been doing, but I am curious if there is a better way to implement this.

    • Hey Charles, we don’t have much solid waste settle out, but what does quickly mineralizes. What doesn’t gets captured by the towers and is mineralized there.

  6. Hi Nate
    I am using hydroton media beds and have found that that the solid waste were not only impeding water flow through the media, but I am cleaning the little sponge filter for the pumps on a daily basis. Finally got around to building swirl filters this weekend. That should help with the media beds. I also removed the pump filters. I think the pumps can handle waste and am hoping the plumbing will handle it as well.

    • Hi Jefferson,
      That will happen. Good luck with your swirl filter. Perhaps you should connect with Jessie (above). She’s working on a filter for a few of her systems and might be interested in any of your insights.

  7. Hi Nate – your videos have been a fantastic resource for me, a faily newb aquaponics grower. I manage 4 different types of aquaponic systems with various filtration set-ups, with a combination of “DIY” type sand media biofilters (which I hate), and fancy parabolic screen filters (which don’t get the small stuff). I’ve been trying to convince the powers-that-be to let me redesign the sand filters to a gravel based media in hopes I won’t sacrifice too much BSA but allow easier cleaning since solids removal has been such a challenge for us. I wish we had the room for settling tanks, but alas, we do not. I’ve also been looking into drum filters, but as a non-profit organization, we don’t have the funds to purchase one. Do you know of a good design for a DIY rotary drum filter? Thanks for your time, and I apologize if this question has already been addressed!

    • Hi Jessie,
      I’m sorry, but I’m not super up-to-date on drum filter design. I know that I’ve seen some details in the literature, but specific articles don’t come to mind. I know that there are quite a few folks working on cyclone filters using 50 gal. barrels with good results, but nothing on rotating drum filters. I can’t imagine they’d be too difficult to build. All you’d need are some drums you could cut up, nylon screening a motor, chain. . . Anyway, I’m sorry I’m not of more help. Let me know if you find anything out there!

  8. Jessie,
    For my solids, I am trying a four foot long piece of 14″ corrugated plastic culvert with the top cut out, with various media type filters, bio-balls, and solid partitions along the horizontal run. It is simple and working well so far.



  1. Building An Aquaponics System: Media-Free Systems - […] necessary in media-free systems; otherwise, solids collect around plant roots and cause problems. Filtration may be passive or […]

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