DIY 20 Gallon Divided Betta Tank

  • #1
Mods, I figured I would put the post here for now, if anyone feels like it belongs in the betta specific forum, feel free to move it

As many of you know, I just finished my divided betta tank that I will be adding my new betta kids to tomorrow when they arrive I have had very bad luck keeping bettas in the past mostly due to the quick spread of disease in divided tanks. Bettas from Petsmart and Petco come with so many diseases that I thought I might have better luck this time around with healthy fish and a more sterile environment for them. Most divided tanks have the dividers that allow water to flow through all compartments, but that also allows disease to spread throughout the entire tank. My design has four separate compartments with a small filter in each one so that if one betta gets sick, I can treat him separately, and the rest stay healthy With all of the betta deaths and illnesses that everyone on the forum has been dealing with, I thought I would share this set-up with you guys.

I usually prefer more natural looking tanks with live plants, but this time around, I decided that I would make sure that all of my decor was betta safe (no sharp edges), so I opted for a different look.

This tank is relatively inexpensive to make, and very easy to do yourself


20 Gallon Long Glass Aquarium (Call around too price them. I called a bunch of different stores and got quoted anywhere from $30 to $80)

Glass Hood (plastic won't work with this design)

Strip Light

4 Small Filters (I like the Azoo Palm Filter, $8.99 from Drs Foster and Smith)

Plexiglass (Purchased at Home Depot for $16)

2 Tubes of Aquarium Silicone (You can get it at Home Depot ($3 per tube) for much cheaper than you can buy it at a fish store)

Glass Marbles (99 cent store: You will probably need about 16 bags)

Plastic Plants (99 cent store)

Margarita Glasses, Glass bowls, or any other glass decorations you want to incorporate in the design.

Black Acrylic Paint and Large Paint Brush
  • Thread Starter
  • #2
Step 1:

Rinse tank and make sure that there is no dirt inside. Let it dry before moving on to the next step.

Step 2:

Cut Plexiglass to size (11.5 by 11.75 inches). If you do not have the means to cut it yourself, Aaron Brothers or any other framing store should be able to cut it for you at a minimal cost.

Step 3:

Open the tube of silicone and cut the tip at a 45 degree angle. Place the plexiglass in the tank (the 11.75 end should be the width, and the 11.5 should be the height) and measure it to make sure that you are placing it exactly in the center of the tank. Use scotch tape (two small pieces) to hold it in place while you silicone everything together. Squeeze the silicone (from the bottom of the tube otherwise the bottom will explode and make a mess) and apply it along all three sides of the plexiglass where the edges meet the tank. I made sure to use a lot of silicone to make sure that each compartment was completely sealed. Be sure that you don’t put any silicone over the scotch tape. Repeat this step twice more to add in the other two dividers. Let the tank sit for 24 hours.

Step 4:

Peel off the scotch tape and apply silicone to the small areas where the tape was. Paint the back of the tank with a coat of black paint (make sure not to get any inside the tank). Let tank sit for another 24 hours.

Step 5:

Silicone any glass decorations that you would like to use in your tank to the bottom of the tank. This will make sure that they don't float when you add water. I used margarita glasses and votive holders to create resting places and caves for the bettas. I chose to use glass because it is smooth and I don’t have to worry about it ripping the bettas’ fins. Add a 2nd coat of black paint to the back of the tank. Let the tank sit for another 24 hours.

Step 6:

Put some silicone on the base of any plastic plants that you plan on using and stick them to the bottom of the tank. I chose to use the silicone because the substrate in the tank is not deep enough to really hold the plants down. Rinse your marbles and add them into the tank as well. I filled up my margarita glasses with marbles too because I liked the way it looked. Let the tank sit for 48 hours.

Step 7:

Put the hood on the tank (leaving the back plastic strip off the back of the hood to make room for your filters). Put the light on the tank. Add your filters onto the back of the tank. Fill the tank with water and add seeded filter media to the filters. Add Prime or other water conditioner to each compartment.

*Make sure that when you fill the tank that you add water evenly to each compartment. Don't fill one compartment at a time because the water pressure could crack the plexiglass or the silicone.

Step 8:

Wait 24 hours and then add your bettas. However, if you do not use seeded filter media, you should cycle the tank fishless before adding any bettas to the tank.

Please Note: I do not use a heater in this design because during the spring, summer, and fall in Southern CA it is warm enough to go without using a heater. I will add heaters to the setup in the winter time. Depending on your climate you will want to add heaters to the setup. You can find small heaters rated for 5 gallon tanks online at many pet supply stores such as petmountain

Please let me know if you have any questions about this set up and I will be happy to answer them. I will post the final picture of the tank filled with water tomorrow once I get my camara charger.
  • #3
nice write-up and nice tank! I kinda wish I had divided my tank using your method, would have saved myself a ton of work!

are you going to keep betta's in each section?
  • Thread Starter
  • #4
Thanks The whole process is really easy, you just have to have the patience to take about a week to finish the tank I am going to keep bettas in each compartment. Infact, they'll be arriving today!!!
  • #5
Did you measure for the inside "walls" just dead on or did you cut then a bit smaller?
  • #6
great write up! thanks for sharing
  • Thread Starter
  • #7
Thanks Alex

Red, I did measure the inside walls. The pieces ended up fitting inside pretty well
  • #8
  • Thread Starter
  • #9
Thank you I'm glad you like it!
  • #10
Ok thanks
Was wondering if you needed some special measurements or not
  • Thread Starter
  • #11
Here's a pic of the finished product:

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