Jump to content

One way to DIY Fry Boxes


Recommended Posts

I had some extra coroplast on hand from another project, so I thought I would try building some fry boxes instead of buying and hacking plastic boxes. Both white and black work. I like the black for aesthetic reasons, but it means an extra step of painting the inside. I have had two boxes running for three weeks and all has been great, so I am making two more.

For this project, I decided I wanted my boxes to fit a 20 long and be 5 inches wide, with a 2 inch water depth. Why? Seemed like a good size! 😄 If you have better reasons for sizes, let me know!

Step 1: Cut a piece of coroplast 11 1/2" (the width of the inner tank trim) x 11 3/4" (3.5 side + 3.5 side + 4 3/4 bottom)

Make sure the "grain" of the coroplast follows the short dimension



Step 2: Create a 1/4" notch on each side, leaving a 3/4" tab on all 4 ends. This is the material that holds the box in the tank.



Step 3: Cut only halfway through each side 3.5" down, and fold up the sides of the coroplast.



Step 4: Cut end pieces, and a small piece to hold the filter sponge/foam.

4 3/4" x 3 1/4" - This is the back wall. The 1/4" gap allows running air/water lines into the box as well as provides an emergency overflow, should somehow the sponge clog. Unlikely.

4 3/4" x 2" - This is your overflow and sets the water height inside the fry box.

4 3/4" x 3/8" - This holds the sponge in place



Step 4: Cut a piece of filter foam/sponge ( 4 3/4" x 3.5" + a tiny extra). Cut it just slightly oversize to create some compression to help hold it in place. The PPI should be dense enough to prevent fry from escaping. I don't even know what mine is. It is pretty coarse, but nobody has escaped yet.



Step 5: Glue in the end pieces. Leaving a little overhang can help you seal it better later. I used water safe hot glue and am curious how long it will last in the long run. Probably better would be superglue+silicone. All good so far though.




Step 6: Glue in the filter retainer. This should compress the foam slightly.



Step 7: Fit and water check.20220219_202111.jpg.3f07b6cbc77fd556d48c8af0a517737e.jpg



Step 8 (optional): If you're using black, dry and paint the inside white. I used Krylon Fusion. It will be impossible to see the fry on black.

Step 9 (optional): Cut some glass or plastic lids.

This is really where my guide ends, as how you choose to pump water and/or air is up to you, but I will show mine anyway.

Step 10: Run water and air (not shown) lines through the 1/4 " gap. I am currently using Tom's aqualifter for water because I had it sitting unused.



Step 11: Add some moss and eggs/fry!


Edited by Vanish
  • Like 10
  • Thanks 2
Link to comment
Share on other sites

The neat thing about this method is you can customize the box to any size. The only tools you need are a razor knife and ruler. Having made them before it only took 15 minutes the second time around. Total cost in materials per box is like $2 to $3.

Link to comment
Share on other sites

This is fantastic! 


Pro tip.  coroplast grows naturally in lawns and road sides.  It usually crops up around election time and can be harvested shortly after elections.

Edited by CT_
typing is hard
  • Haha 4
  • Love 1
Link to comment
Share on other sites

On 2/19/2022 at 3:37 PM, CT_ said:

Pro tip.  coroplast grows naturally in lawns and road sides.  It usually crops up around election time and can be harvested shortly after elections.

I am not sure that I would want to use political signs in any of my tanks. The residue from those things are toxic!

  • Haha 4
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Create New...