Introduction: DIY IMac Fish Tank

About: Pinterest engineer by day, maker by night. Member of the Noisebridge hackerspace.


approximate costs in USD

- 1/4 inch thick clear acrylic ($40)

- fast set Weld-On 4 with applicator ($10)

- thicker Weld-On 16 tube ($6)

- [OPTIONAL for changing the water by siphon] 1/2" (outer diameter) vinyl tubing


- laser cutter (really expensive - find it at a maker space)

- FLAT silicon plastic heat strip ($50, and this is the specific one I have

This Instructable assumes that you have an iMac G3 that you've taken apart. From the iMac you will need FIVE PIECES:

- bottom white plastic case piece

- front white plastic case piece

- back colored plastic case piece

- metal tray that goes on the bottom of the computer

- metal platform that the monitor sits on top of

If you have a computer that has not been taken apart, check out my instructable here:

Getting access to acrylic sheet and a laser cutter sounds hard, but I've lived in Toronto, New York, and San Francisco, and these things were accessible in all three cities. Ask the maker space that hosts the laser cutter - you will likely be required to go through some sort of safety training before being able to use it. You may also be able to convince a kind maker space member to help you cut your acrylic for you.

Toronto: Plastic from Plastic World (, laser cutter at HackLab (

New York: Plastic from Canal Plastics (, laser cutter at NYC Resistor (

San Francisco: Plastic from TAP Plastics (, laser cutter at Noisebridge (

I haven't used the laser cutter in Toronto, but I've bought plastic at all the places listed and used the laser cutter at NYC Resistor and Noisebridge.

If you LOVE this project and want to read my project diary, it's on Medium:

Step 1: Buy Your Plastic

The tank is made with three pieces of plastic:

- the front-and-sides (this is one piece of plastic with two bends)

- the bottom

- the back

Here is the laser cutting file so you can see the sizes of all the pieces. If you are buying one piece of plastic and your laser cutter is bigger than 4 feet wide, you can get one piece. If you have a smaller laser cutter or are bargain hunting in your plastic place's offcuts bin, you can get multiple pieces. For this project you will need:

one 4 foot by 1 ft piece (if your laser cutter bed is at least 4 feet wide)

OR two pieces: one 29"x10" piece and one 21"x10" piece

OR three pieces: one 29"x10" piece, one 13"x9" piece, and one 8"x10" piece

Note that these are minimum sizes, not exact sizes. You want 1/4 inch thick clear acrylic. It doesn't matter whether it's cast or extruded (I just buy the cheaper kind). If you are getting it from the offcuts bin, beware that it may be scratched. Acrylic scratches easily. If you care a lot about scratches, your plastic store can probably recommend you some acrylic scratch buffer stuff.

Step 2: Laser Cut Your Plastic

Use the attached vector file to cut the pieces on your laser cutter.

**If you are not making the siphon, be sure to delete the blue circle so you don't cut the siphon hole in the back **

If you have a big 4 foot by 1 foot piece like I do, you may have to cut your plastic scrap in half so you can store it.

Step 3: Bend Your Plastic

I used a Sharpie to draw a line where the bend should be. If you don't have the nice right-angled ruler that I have, you can measure where the line should be. The top of the line is 7.5 inches from the side, and the bottom of the line is where the bottom corner is.

To make the bend, I laid my plastic heat strip so that the line was centered under it. I put a piece of wood on top so that the strip would be in contact with the plastic. Be careful to make sure the strip hasn't shifted after the wood is placed on top - I have made this mistake, resulting in bends that weren't exactly where I wanted them.

Wait 45 minutes for the plastic to heat up and soften. After 45 minutes, take something that doesn't melt and has a right angle (I'm using this piece of wood), and line the edge of it up with the line. Bend the plastic against your object.

Now that the bend is in the right place, you want to make sure it's at the right angle. Use the piece of plastic for the bottom of the tank as a template to get the angle right. Work quickly - you want the plastic to be hot and pliable so that you can easily get the angle correct. Keep holding it at the angle you want until it holds its shape well (~10 minutes).

You will be making two bends, one for the left side of the tank, and one for the right side of the tank.

Step 4: Melt the Contact Edges Flat

This is where the flatness of your plastic heat strip comes into handy! Before you attach the back and bottom to your front-and-sides piece, you need the contact edges to be flush. Leave the edges on your hot plastic heat strip. I've weighted mine down with some fabric weights filled with rice. If you have a paperweight or similar, you can use that too. No weight is also OK, but it might take longer to melt flat.

You want to make sure that the following are flat:
- the two edges on the front-and-sides that connect to the back

- the bottom of the front side

For the back edges it took me about an hour to melt each edge. For the bottom of the front side it took several hours.

Step 5: Weld the Back to the Front-and-sides

Weld the edges with Weld-On 4

I am using the pin method described on the Advanced Aquarist website:

In my pictures you can see that I did this without tape, but I wish I had used masking tape or painters tape for this step and the next step, just to prevent things from moving around by accident. Position yourself at an angle that allows you to see the solvent seeping into the gap, so you can make sure you're not leaving any big bubbles.

Next time I do this I also plan to only use the tip half of the pin. If you put too much solvent (which I did), it travels up the tip and marks your plastic where the pin was.

If you have chosen to include the hole for the siphon, the hole is closer to the top of the tank than the bottom.

Tip: I had a really hard time opening the metal lid of the Weld-On, and after hacking two holes into it with a knife, I discovered this video which shows you how to open it properly:

Step 6: Weld on the Bottom

I used the same pin method as when I attached the back. It's hard to get the bends perfect (and it's fine if they're not perfect), but for this step you want to make sure that the bottom is positioned such that the bottom edge of the front-and-sides is touching it all the way around. Better to center the bottom piece and have the front-and-sides sticking out a little on both sides than to align it perfectly on one side but have a leak on the other side. Again, I wish I had taped it because it was easy for the plastic to accidentally shift while I was working on it.

Step 7: Fill in Gaps

Fill gaps or bubbles with Weld-On 16. This stuff is thicker and comes in a tube. It comes in really handy if in the last step you weren't able to quite make the acrylic edges perfectly flat and flush against each other, because it won't seep back out of the acrylic gaps. It's also handy for filling in large bubbles.

Inspect the welded edges as best as you can to make sure that there aren't any gaps or dangerously large bubbles before moving on to the next step.

Step 8: Leak Test

I leak tested my tank overnight by leaving it filled with water, and checking to see if it leaked.. I recommend this as the water pressure may take a while to make any leaks obvious. If you have a leak, see if you can fix it with more Weld-On 16.

Step 9: (Optional) Add Siphon

Take your 1/2 inch vinyl tubing and put it through the hole in the back. The end that is in the tank should be threaded all the way to the bottom. If you want to have gravel, you can put the tube under a plastic craft mesh, and your gravel on top of the plastic craft mesh. This way waste will drop through to the bottom where your siphon is. The outside end of your siphon will drain the tank if the height of the end is lower than the height of the water.

Step 10: Celebrate

You did it! People on certain reef forums who make acrylic parts all the time for their tanks claim that you only have to wait a couple hours after plastic welding for your tank to be fish safe. I waited a day. If you are not taking the time to nitrogen cycle your tank, be sure to get one of those products with bacteria to start of the nitrogen cycle.