Project: 350 gallon plywood tank


Feeder Fish
MFK Member
Aug 22, 2008
Edmonton, Canada
Well, its finally done. I want to say a big thank you to the members of Monsterfishkeepers. Your DIY ideas and discussions were inspirational!

This is the first time I have ever tried something like this. After much research and thinking I decided to line the tank with pond liner rather than use epoxy (I had to build this in the basement and I have heard the epoxy fumes are terrible so I chose the pond liner).

I used the plywood and acrylic plans that are available at

The tank is: inside dimensions 94.5" x 36" x 24" (353 gallons)


The cat was no help in this project :lol2:

3 sheets of marine grade plywood (had the store cut the wood for me)
9’ of composite decking plank (had the store cut into 3, 3’ lengths)
¾” clear acrylic
2 boxes of 6 x 2” drywall screws
1 bottle of Titebond III (a wood glue that is waterproof, has a strength of 4,000 PSI, and is FDA approved for indirect food contact)
Loctite® Super Glue
16’ of 1 x 2 spruce lumber
Finishing nails
40 mil EPDM pond liner
3 tubes of silicone (GE Silicone I Window and Door)
Exterior wood varnish

Assembly of the tank

I had the first 8’ sheet of plywood cut to 37.5” to ensure the inside dimensions of the tank would be 36” wide. With the help of my husband I attached the back sheet to the bottom (as in the garf instructions) added a bead of wood glue, placed the screws at 3” intervals, and wiped off any excess glue. I then did the same thing for the two side pieces.

The front was a bit more work. The plywood store cut the front piece but were unable to cut out the viewing area. I measured the front to ensure that there would be a border of about 2” around 3 sides and 8” on the left side (I am installing a filter in the tank that will take up that space). I cut out the area for the acrylic and then attached the front piece to the tank.

I then varnished the entire tank both inside and out. I did 3 coats on the outside (sanding between each coat) and 2 coats on the inside.

I then put the pond liner in and made sure it fit flat on the floor of the tank. The big challenge was how to put in the acrylic window and not have it leak. First, I attached the acrylic to the pond liner using a super glue that I tested on some scrap pieces of acrylic and pond liner and it worked well. Then I found an idea on a forum (don’t remember which one now) and modified it for my needs. I sat the acrylic in the tank on the pond liner and then placed the 1 x 2 lumber under the pond liner as close to the acrylic as possible. I then filled the area on all 4 sides between the pond liner and the acrylic with lots of silicone (both on the inside and the outside).

The acrylic is behind the pond liner. I had to fold the pond liner over the acrylic to properly place the 1x2's

In order to make sure that the silicone would not pull away from the pond liner or the acrylic, I sandwiched it between the acrylic, plywood, pond liner, and 1x2 lumber.

I then did a second layer of silicone on top of the one that was sandwiched in order to have a nice finish.

I filled the tank partway to see if there were any leaks. There was a very small one so I emptied the tank, found the leak, fixed it and, after letting the silicone dry, started filling again. This time there were no leaks so I filled the tank and let it sit for about 4 hours. There were still no leaks so I emptied the tank and added the deck planks to the top as braces.

The tank has been up and running for over a week now and everything is going well. It is taking awhile to fully fill as my holding container only holds 50 gallons at a time, but it is nearly there.

I hope you enjoy this post as much as I enjoyed building the tank!

bOOsteN aUdI

MFK Member
Apr 1, 2005
East Coast
looks great! i always though about making one of these but don't know what the life expectancy is on a GARF tank is. If you don't mind me asking, was it still expensive to build?


Feeder Fish
MFK Member
Mar 23, 2007
Monroe, Wa
what are the dimensions? looks really nice.


Fire Eel
MFK Member
Sep 3, 2008
Brisbane, Australia
why didnt u go bigger i have a 350 and i carnt help but think its to small so over the next yr ill be building a gal steel framed 3000g plus a 1000 or 500 g sump

also whats the life on the black plastic?