Betta suddenly timid and jumpy

[GobyMaster11276]

So, we went away for the weekend, and when we came back Apollo, my sister's betta, was suddenly acting very jumpy and timid. He always retreats to the back of the tank, hiding behind the plants out of view whenever anyone comes toward the tank.

While we were gone, our mum was left to feed the fish, but she didn't (due to confusion about feeding amounts). This led to him missing two meals. No loud music or other noises were made during this period either.

My sister sat and watched the tank for a while earlier, waiting for him to swim out. He eventually swam up to the surface to get air, and she stood up from her seat to put food in the tank. The sound of her getting up alone was enough to make Apollo immediately go back into hiding. This has been making feeding very difficult as he won't come out while we're present. At the moment, food is being dropped in, and after a while of no-one being nearby, the food disappears (we have checked, but not at the bottom).

Does anyone know what could have caused this behaviour change, or how we could fix it? Thanks in advance.

 

[betta fish]

You'll need to give us a bit more info as to size of tank, location, decor/plants, temp, filter, etc also how long have you had him? a pic will be good and we can go from there

 

[GobyMaster11276]

We have had Apollo for a few months. It is a divided 70 (or 75, can't remember) litre tank. That makes Apollo's side about 35l. My betta lives on the other side of the tank and is still completely normal. Apollo's tank is mainly planted in the back half, with long tall weedy plants. The front has small, shrub-like ones, and a hiding cave in the middle. It is located against one of the lounge room walls next to a window (but far enough not to get direct sunlight). The tank is around 26 degrees celsius. There is a corner sponge filter on either side of the tank, but I can't remember the brand (we got them a while back). Hope this information is useful. I can't get a pic right now, so I will try get one tomorrow. Any advice will be greatly appreciated.

 

[betta fish]

Is Apollos side closer to the window or further away? it could be that he is nervous of the other betta if he can see his shadow through the divider, perhaps try swapping sides and see if that helps or planting across the divider to break up shadows.

 

[GobyMaster11276]

Apollo's side is nearest to the window, but I don't think that they can see each other because the divider is completely black with only a few holes drilled through. Occasionally, they both flare at the divider, but I supposed that they can hear each other. I will get a picture later today so you can get a better idea of how the tank is. Thanks for the help so far.