Backyard Aquaponics
A place to discuss aquaponics

Hey everyone, I remember reading some suggestions that mechanical filters were not needed and that a sufficiently deep media bed with composting woms added was a better way to go for nutrients and mineralization, yet most systems I find on here or on YouTube seem to have some kind of additional solids filter involved.

I couldn't find anything on this topic sear hung the forum, but wondered if I might be able to ask for some links (or explonations) to both arguments, and sizings / ratios to consider for either approach?


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Hi there,
I run a radial flow filter before my grow bed in one of m/y systems. I like it simply for the fact that it keeps major solids out of my grow bed. I also have worms in the grow bed, and they are thriving on whatever gets in there and decaying root matter. My main logic was to slow down the time between deep cleanings. I have a feeling that the media that I chose (Perlite) traps gunk quite well because the individual rocks cling together quite well.

I used a blue drum to make it, and I looked at retention time info when I constructed it, but I've honestly forgotten all of that! It does work quite well at removing solids. Now that this system is around a year old, I am not seeing much in the way of deficiencies. Though I did see some when it was a younger system as most folks do.

It's pretty straight forward so I'll try and explain the reasoning.

If you have a a relatively light fish load, media beds are sufficient because you won't get a lot of solids build up. The media beds provide solids filtration, biofiltration and mineralization.

If you are trying to push the limits and grow lots of fish then the solids can accumulate in the grow beds faster so you would probably benefit by adding a Radial Flow Filter or some other type of solids filter. This will slow the accumulation of solids but requires that you regularly empty the RFF. These types of filters provide mostly solids filtration so you are still leaving biofiltration and a portion of mineralization to the grow beds. Some nutrients are lost when the solids are removed from the system.

I am also considering adding some kind of moving bioreactor, because I'd like to stock a little higher fish load.

Is it possible to reintroduce the nutrients from the solid waste after breaking it down. Example: can you feed the solid waste to black soldier fly larvae, then supplement the fish feed with the larvae. (Unsure if the would eat the waste, maybe another organism)

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This is true Justyn. It would be an interesting experiment. My fish have shown interest in bsf larvae when they are cut in half. A nice way to keep nutrients in the system.

There are all kinds of different ways you can cycle the nutrients either back into or out of the system. Fish could eat BSFL or worms grown with waste or Chickens would eat worms and BSFL, they lay eggs and the eggs can be fed back to the fish. You could also just use the waste on your soil based plantings or add it to a compost heap.

If you don't have enough plants and can't add another grow bed for space reasons you can use Water Hyacinth, duckweed, or azolla to filter excess nutrients from your AP system (be sure they are legal in your area). Just remove them to the compost pile if they start using too many nutrients. The worms or BSFL can feed on them in the compost pile.

Are there any pond plants like you mentioned Scotty that grow well in shade? I would like to try something like that in my sump, which is under a grow bed and gets limited indirect light.