Well the first fish that was in the tank seems to be ignoring the new one while the new one is getting desperate to go to the other side. Should I let them divided like that or should I put one back in a 1 - 1.5 gallon fish bowl alone?
It really depends. How long have they been in the tank together? Do you have a store bought or homemade divider? Do you have any plants or decorations around the divider to help beak up the line of site?
i have decorations around, it is a homemade divider, they've been in the tank for 10 minutes and the new betta just broke through. I put him back in the fish bowl and im buying him another 5 gallon today
It depends. I would be a bit more careful with a tank of halfmoons or deltatails or something because they have such heavy fins that over working can lead to torn fins but IME dividing the tank was beneficial. It gave both my boys something to do, they flared constantly at each other for the first week and half or so. They built nests and guarded them. Now they mostly ignore each other, however, they will flare if the tank light is off but a light in the room is on because it causes reflection on the glass in the tank and they go at it.
It helped my VT because before the divided tank he bit his tail. He has not bitten since the divider.
To prevent one jumping onto the other side during the initial period, lower the water level a bit.
I say leave them in the 5g and see how things go for a week. It is recommended you block off the divider on both sides at least partially with plants or a decoration.
Nice tank!! *it's not a nano tank so you can haggle the price ;D
And be careful with the gravel, wash everything with a mild bleach solution and rinse VERY thoroughly!
What kind of divider were you using that he was able to squeeze through it?
I think both fish will be very happy in their own 5g !