Housing 3 male betta fish in 1 ten gallon tank

Step 2 Adding the bettas...

Once the tank was ready, I put each betta into his compartment.
The tank measured 20" wide, 12" top to bottom, and 10" front to back.

I made the center area 7", a little larger than the side areas (6.5"), so that the filter
would have plenty of room.

This was a serious upgrade in size and water quality for the bettas !
10 filtered gallons vs. about 4 unfiltered gallons (between the 3 vases).

After all 3 were transferred, they could see each other, and started getting mad.
I couldn't get a good picture because the dividers are clear, and the fish were very angry and swimming around very fast.

They couldn't get to each other, so I left the light off and kept the room fairly dim to see if they would get used to each other.

The next day I called every aquarium shop and pet store that I could find, and they all only
had the clear dividers.

This may work for other fish, but not for male bettas !

After 2 days, they were all the same. Mad, tired, mad, tired.....
It looked like the clear divider material wasn't going to work out.

I tried getting different types of material and drilling holes in it, but that was very time consuming.
First you have to find a thin rigid opaque plastic, drill tons of holes in it, then go back and smooth out the exit side of the drilled holes so that your fish don't get scratched up if they brush against the divider.
My experiments looked bad with just a few holes drilled, so I scrapped that idea.

After some thinking about materials with holes already in it, I came up with an idea that would solve my problem !