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How to DIY an aquaponic filter cheap

growing with aquaponics

Aquaponics is growing plants with hydroponic methods and using fish tank water as a grow solution, ie. fertilizer. Here are some tips on how to DIY an aquaponic filter cheap. This is based on what I use.

I love aquaponics because it is practically a self-regulated system. It requires very little work from me. The best part is of all the systems I have had over the years the aquaponic system consistently grows the biggest healthiest plants.

DIY Aquaponic filter

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The filter has two major functions:

  • To filter particles out of the water.
  • To change the ammonia to nitrates

There are a lot of complicated commercial and homemade systems. I have tried several different varieties. I have designed a super simple and very inexpensive that anyone can make in just a couple of minutes.

The basics of my aquaponic system use:

29-gallon standard fish tank

special homemade filter (see instructions below)

an 8’ long, 1’ wide, 4” deep growing table lined with plastic

Standard fish tank heater

Pond pump strong enough to lift the water to the height of the table

½ inch flex feed line from the pump to the filter

¾ PVC return pipe

8 Goldfish

The how to DIY an aquaponic filter cheap

The filter that I will explain is the same one that has work great for me for years.  However as you can see I did originally use a much smaller container than I do now.  This is because I switched me fish from Mollies to Goldfish.  Goldfish provide much more nutrients to the system in the form of ammonia.  This increase in ammonia required a bigger filter.

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My small filter

DIY filter

How did I know I needed a bigger filter?

My fish tank water was always cloudy, my PH levels were fluctuating at lot and my plants started to grow poorly.  Each one if those things would be a sign that you need to change the size of your filter.

Since the change in size several months ago, I have not cleaned the fish tank.  I have rotated thru about 5 crop cycles of great greens!

how to DIY an aquaponic filter cheap

How to DIY an aquaponic filter cheap for bigger fish

First, do not leave the standard fish tank filter in the tank!

What you need:

A pump. Use a pump the is rated to lift the height raise between the bottom of the tank and the top of the filter

Use a ½ feed line from the pump to the filter. I find ½ allows a good rate of water flow. The pump size will affect the rate of flow also.

A container that will fit your system’s needs. The large food storage container work fine while I had Mollies.  Now I use a plastic file box.

How to

Take a large plastic container with a lid.

Drill or cut a hole in the lid for the ½ inch feed line. This hole doesn’t need to be perfect. It just needs to be snug enough to hold the line.

Drill or cut 2 – ½ holes in the side of the container about an inch from the bottom. These holes don’t need to be exact if they are draining directly into your grow table. If you are using a PVC tube or gutters, make sure that you have holes that can be made watertight. The important things to remember about the outlet hole/holes is that it is/they are twice as big as the intake. This will prevent overflowing.

Fill the plastic container with a filter medium. I have had great success with using old synthetic loss pillow stuffing! Any kind of synthetic fiber will work as long as it is individual fibers.

how to DIY an aquaponic filter cheap

Do not use foam rubber or solid foam!

Fill the container to the top, pushing it down as you fill. The filling should fill all the corner and be very full. As the fibers get wet they will condense and the box will end up with an air space at the top. This air space is needed.

how to DIY an aquaponic filter cheap

You need to add a bacteria enhancement.

This is available anyplace that sells fish supplies. You can let the bacteria grow naturally but that could take several months. The system will be ready right away with several drops of bacteria enhancement. The fibers will turn dark brown or black. This is normal and good. The brown color is the bacteria doing its work.

bio boost for fish

The air pocket that forms between the lid and the fiber is important because the bacteria are alive.  The bacteria need air the breath, so makes sure there is a void.  Leave the lid lose or cut additional holes in the top to vent.

Do not put the feed line deep into the container.  You want the water to empty from the feed line at the top of the fiber.  This will allow the water the be filtered thru all the fibers before coming out of the bottom.

The last thing that you need to do is cover the container.  Sunlight will encourage the growth of algae in the filter just as it would in your tank. Any covering will do.

how to DIY an aquaponic filter cheap

That’s it!

You should never have to clean the filter or add anything to it once the bacteria has started to grow.  So now you know how to DIY an aquaponic filter cheap

The filter will naturally make the water plant-friendly.  The plants will clean the water for the fish.

how to DIY an aquaponic filter cheap

It is a perfect self-sustaining, no maintenance system.  You may have to do a bit of adjusting with the size of the filter depending on the number of fish. The file box size works well with the 29-gallon tank.  There is a lot of wiggle room in the system so adding or losing a few fish shouldn’t make any difference.

Thanks for reading. Please let me know if you have any questions


how to DIY an aquaponic filter cheap


To learn more about why fish water is so good for plants read “how to grow the best plants with fish water”

Also check out more about grow mediums.  That is what to put you plants in to hold them up

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This Post Has 4 Comments

  1. Other articles I have read leave me feeling overwhelmed. Yours is great and I am going to try your method. Do you have any pictures that show your whole filter? I am wondering how you have the bottom of your filter box for the water to drain out?

    1. Thanks so much! I am glad it was helpful. Have fun! I added a picture to the end of the post on the bottom of the filter. Please check it out

  2. Hi, I am more of a show me step by step type of person. I get most of what is being done but I feel a little lost in the middle. Do you have any videos that may help me? I have been looking and researching for a while and so far, I like yours the most.

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