Easy and cheap DIY aquaponic filter

Aquaponics is a method of growing plants; however, with aquaponics, you are using fish tank water as a grow solution, i.e., fertilizer.  There are lots of costly and complicated filter systems you can buy.  If you know me, you will know that I don’t like spending a lot of money on something I can make myself.  This guide to an easy and cheap DIY aquaponic filter is one I have successfully used for years.

Easy and cheap DIY aquaponic filter

I love aquaponics because it is practically a self-regulated system, requiring very little work from me.  And the best part is the aquaponic system consistently grows the biggest healthiest plants.


The need for an aquaponic filter in your plant/fish system.

Direct planting on a fish tank

You can just put plants roots directly into a fish tank.  I have done this many times and have found it works best for small plants in, short term.


Because aquaponics works so well that every time I put plants directly over a tank, the plants take over the tank!  The plant roots will grow so dense that the fish will get tangled and die or not have enough room to swim.

 DIY aquaponic filter

Direct planting over a fish tank is super helpful to bring sick plants back to life.  The high volume of easy to get nutrients will help give your plant a healthy boost to overcome any deficiency.  If you have soil plants that you don’t want to convert to aquaponic plants, then use fish water to water your plants instead of plain water, and you will see a difference quickly.

A full aquaponic system will have room for your plant’s roots to grow and your fish room to swim.

The aquaponic filter has two major functions:

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

I have designed a super simple and very inexpensive that anyone can make in just a couple of minutes.

The basic Easy and cheap DIY aquaponic filter

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

The filter that I will explain is the same one that has work great for me for years.  However,  I did originally use a much smaller container than I do now.  This is because I switched my fish from Mollies to Goldfish.  Goldfish provide much more nutrients to the system in the form of ammonia, and this increase in ammonia requires a bigger filter.  Size your container in line with the amount and kind of fish you have.  This can be a bit of trial and error, but too big is always better than too small.


How did I know I needed a bigger filter?

My fish tank water was always cloudy, my PH levels fluctuated a lot, and my plants started to grow poorly.  Each of 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:

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

What you need:

A pump. Use a pond pump that is rated to lift the height between the bottom of the fish tank and the top of the filter.  A little bigger, or higher, the lift is much better than not having enough lift.

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.  The small pond pumps are set up to take 1/2 feed line.  This type of feed line can be purchased where you get your pump. Underground water irrigation line will work but is often stiffer and harder to work with than pond tubing.

A container that will fit your system’s needs. The large food storage container worked fine while I had Mollies.  Now I use a plastic file box.  The file box is great because it is stronger than food storage containers, and the lid stays in place better.

FILL. use a loose fiberfill

How to

Take your 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 in place.

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 thing to remember about the outlet hole/holes is that it is/they are twice as big as the intake. This will prevent overflowing.  This is the reason for 2 holes out with one feed line in.  You never want to come home to a flood!

Watch the video to see my trick to ensuring that it never overflows!

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.  Don’t use a solid material.  You need to have lots of air pockets and easy water flow.

Fill the container to the top, pushing it down as you fill. The filling should be stuffed all the corners and be 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.

You need to add a bacteria enhancement.

This is available at any place 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, and the brown color is the bacteria doing its work.  Sometimes the fish store will give you some for free!  If you need to purchase some, try this.

The air pocket that forms between the lid and the fiber is important because the bacteria are alive.  The bacteria need air the breathe, so make sure there is a void.  Leave the lid loose or cut additional holes in the top to vent if you are unsure about the airflow.

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, and just keep the sunlight out!

That’s it!

The easy and cheap DIY aquaponic filter will be the starting point of a great aquaponic system. You should never have to clean the filter or add anything to it once the bacteria has started to grow.  This will work regardless of the kind or amount of fish or the type of setup you have for your plants…..I have even used this same basic setup with ducks and a greenhouse!

Thank you for reading.  Please let me know how your filter works out. Please read more about hydroponic indoor gardening here

And don’t forget to visit our store to get the best grow lights on the market!




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