Fluval Flex Inlet Covers

Here are my versions of the Fluval Flex inlet covers that give better coverage around the sides.
These where made to fit the Fluval Flex 57L (15 gal) version, and I can't confirm if they fit the other sizes of aquariums.
If you try them for the other sizes, please leave a comment so that others might know if they work.

The original covers can be made somewhat shrimp/fry proof by adding foam to them, but the way they are designed there will be small gaps on the sides since they don't extend over the inlet slots.

My versions also require foam to be shrimp/fry safe, but they overlap the sides.

I've also included a foam cutter/template to make matching foam inserts.

Updated 2025-10-21

I noticed after several years that the covers where more easily coming loose. So I made new versions of all that have slightly longer barbs (the ones that hook onto the inlet).
If they are to hard to snap into place you can trim a tiny amount of the barbs off.

The new versions ends with “longerbarbs” in the filename.

Updated 2020-06-16

I noticed that the fit on the bottom inlet doesn't actually match the top inlet, so the original design wasn't fully compatible for both inlets. So I tweaked the cover for the bottom inlet and renamed all of the files.

There are different versions of the covers:

-TopCovered: Full size cover that is tall enough to cover the top inlet. The top half has smooth sides to prevent shrimps from climbing over the cover and into the first filter chamber.

-TopFull: The same size as the TopCovered one, but has holes all over the surfaces.

-Narrow: For the bottom inlet. Has the same height as the Fluval original covers which will still cover the entire bottom inlet.

-Narrow_V2: Same size as the regular "Narrow", but I couldn't decide on the orientation of the hexagonal holes.. So this one has them rotated 30 degrees.

Foam cutter/template:

-The interior perimeter is the correct size to fit the full size covers.

-The "Narrow" markings indicate the size that should be cut to fit the narrow covers.

-It requires a 18mm snap off blade in order to slice the foam horizontally to the correct thickness. The blade just slides into the slots.

Print Settings

Printer Brand:

Prusa

Printer: 

I3 MK3S

Filament: Prima PETG 
 

Notes:

When printing with PETG I get much stronger layer adhesion by printing with the part cooling fan turned off.
Doing that will lower the risk of the clasps snapping off when they flex into the inlet slots.

Make sure to use filament that are safe for food/beverage contact (I used FDA approved PETG).

Post-Printing

I let the parts soak for at least 24 hours in a tub of hydrogen peroxide/water solution to clean them off.

Then rinse them before adding them to the aquarium.

The hydrogen peroxide is probably overkill, but hey.

How I've sliced my foam:

Naturally, be careful...

You might want to use cut resistant gloves if holding the foam like I do. Or use something else to hold the foam steady while cutting.

When the foam is cut to size just put the foam on top of the covers clasps, find their location and cut slots for the clasps.

Category: Pets