Can we build an open hardware expandable filtration system to keep our aquariums clean with little maintenance?

You can get all of the relevant linked_files for this project at the bottom of this post

So I have two messy turtle pets that love to eat but don’t like to clean up after themselves :). In the past, every so often I had to take a few hours on the weekend to dispose of the dirty water and clean up the tank thoroughly, then fill the tank again with clean water and put the turtles back in. This was a wasteful, inconsiderate (clean water is a limited resource, more so here in CA) and time consuming process.

Much like other aquatic pet owners I wanted a better alternative and also I wanted to learn a bit about CAD tools and 3D printers, it seemed like the perfect opportunity to kill two birds with one shot.

With a bit of research I discovered that there are different kinds of water contaminants, what you see is only half the story (i.e. large dirt residues) for example there are chemical contaminants that can become toxic in large concentrations without you ever noticing. Therefore in order for a filtration system to be efficient all of the types of contaminants need to be considered. In my case I decided to remove the contaminants by utilizing multiple filter stages. It turns out that this is exactly the same approach that aquarium canister filters use, that was reassuring, at least I was on the right path.

I settled on a very common filtration setup that seemed to be effective with commercial filters with the option of increasing the number of stacked stages as required to increase the efficacy of the filter:

Stage 1: Filter Head Mechanical filtration, cleans up large dirt residues, keeps pump healthy and keeps the fine mesh filter (Stage 3) unclogged.

Stage 2: Pump. The pump will be our second stage pumping the water up to the other filtration stages, the pump stage needs to be submerged in the water.

Stage 3: Fine Mechanical Filtering Cleans up Small particles, mesh is fine pitched (e.g. like coffee mesh )

Stage 3: Chemical Filtering Activated Carbon to remove toxic chemicals from tank.

Stage 4: Biological Filtering Porous Ceramic Rings to provide the environment for healthy bacteria to grow. At this point the water should be relatively clean.

On top of the multiple filtration stages I wanted the filter to be placed inside the tank to have the ability to work like a floor vacuum. Say for instance if dirt accumulates in one corner of the tank you just do a quick floor sweep and bingo the house is clean :)

So at this point I had lots of design drawings and a rough idea about the inner details of each individual filter stage, all in text linked_files and sketches (b.t.w check out xournal is a pretty cool open source hand notes suite for linux, kind of like OneNote for windows users).

Time to start the quick mechanical prototyping to identify the winner designs, but there was a problem: no 3D printer yet, plus it seemed every print was going to take forever and I had lots of little small ideas I wanted to try out. I wanted some sort of  non-toxic water safe, stackable structures that I could actually test out in the tank itself, any ideas?

I’ll give you a hint: it involves overpriced plastic bricks, hehehe Legos! Oh how they bring back good memories!

So for a while I tried multiple stackable geometries, multiple stages and filter media. Leaving  the test setup in the tank for a few days at a time to see it’s effectiveness and make new improvements.

Finally with some rough technical specs in hand I was ready to start the CAD modeling and bring the aquarium filter to life. In my search for a CAD modeler, I found an awesome open source 3D CAD suite (

Learning to use FreeCAD was very rewarding, while the learning curve was steep seeing the sketched models with all the specs come to life was really exciting.

Having the first drafts of the 3D models ready, I needed a 3D printer to proof the concept and tweak the final designs to be suitable for long term use. The Printrbot simple kit seemed like a good candidate for my purposes,  the assembly, calibration and setup of the 3D printer are described in one of my previous posts.

After two spools of PLA (I put some research to understand potential toxicity concerns in water, here is one interesting post: and lots of fine tuning in my models (getting the stages to be lego compliant was kind of a pain: close to the bed the plastic expands and at the top it cools off and contracts) I got the final design up and ready.

Alright so at last to the substance of this post, here is the meat and the veggies :)

All of the CAD resources can be found in my water filtration github repo

e.g. If you want to test drive the filter system you can browse to the individual filter sub-directories, and simply use the .stl linked_files to 3D print the filter sections.

You will also need the following inexpensive items:

  • Fine filter mesh: e.g. Marineland PA0100 Bonded Filter Pad, 312-Square-Inch.

  • Biological filtration media: e.g. Fluval Biomax Bio Rings - 500 grams/17.63 ounces.

  • Chemical Filtration media: Activated carbon, e.g. Fluval Carbon, style C3.

  • Water Hose:  Silicone Tubing 7/16-Inch OD x 5/16-Inch ID

  • Water pump: just a standard aquarium water pump (mine is just a cheap one from e-bay)

The final filter sections are arranged as follows (starting from the bottom of the tank to the top), each section with pictures:

sorry for the water, i took the pictures during a quick filter cleanup.

Turtles Filter Head 1

Function: Large mechanical Filtration

Filter Head 1

Turtles Filter Head 2

Function: Large mechanical Filtration

Turtles Filter Head 2

Turtles Filter Head 2

Turtles Pump Stage

Function: Housing for the pump

Turtles Pump Stage

Water Pump

Turtles Filter Stage 1

function: Biological Filtration

Turtles Filter Stage 1

Turtles Filter Stage 2-Chemical

function: Chemical Filtration

Filter Stage 2-chem

Chemical Filtration Stage

Turtles Filter Stage 2-Mechanical

function: fine mechanical filtration

Filter stage 2 mech

And that’s it those are all the stages of our filter: Filter Head 1, Filter Head2, Pump Stage, Filter Stage 1, Filter Stage 2-chem, Filter Stage 2-mech.

Complete Filter (Dirty after one month)

Now here are some pictures of the dirty filter after operation for around one month.

Filter Dirty 1

Dirty Filter 2

Complete Filter (Clean)

right after cleaning all of the filter sections.

Filter Clean 1

Filter Clean 2

In conclusion, the filter works better than I would have ever hoped for!

Enjoy and share with others :)

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