Betta looks bloated and not moving or eating???

Had this Betta for a few weeks, we saw it in the shop and my wife loved it, she’s not usually interested in my animals, so I bought it, and put it in a 160l tank I had already running until my smaller tank was cycled, in the 160 the betta was active and seemed healthy, but the leopard danios I have in that tank are super nippy, so as soon as the tank was cycled I moved the Betta over. The new tank is 30cmx25cmx20cm I think, which I know is on the small side, but I’ve read works for a lot of peoples bettas. I’ve been keeping fish for a long time and have done daily 30% water changes, so I struggle to imagine that nitrates are the problem. All of a sudden, a few days ago the Betta stopped eating, and is now looking really unwell. I tried feeding blood worm, which disappeared over a day or so, which I assume means they were eaten, but they weren’t taken with any enthusiasm, and the Betts seems unhealthy. Any help would be greatly appreciated, would be nice if my wife’s first fish didn’t die so fast

My guess is that your smaller tank is not yet cycled. I'd get a breeder net and put it in the big tank today, and place the betta in there.

The way you describe how it happened. I'm incline to think that your betta has been seriously overfed.

The sluggish behavior is similar to us lazing around after bingeing on thanksgiving dinner and might have caused constipation. If there's cods and pods in the tank, he might have feasted a little too much on them.

I would fast him for a week and on day 4 offer a single pealed canned pea.

Observe the fish often, try to find poop and check if it is looking normal. It can also be caused by internal parasites.

Make sure that ammonia and nitrite are not rising and water quality remain pristine.

I just took another look at the photo. Although it’s a bit blurry there’re 2 things concerning.

1) Are the bubbles on the water surface from the fish gills or from the filter? If from the fish then it’s bad news as that happens when a betta struggles to breathe. Bubble nests that bettas make when they breed are different, the bubbles are not scattered on the water surface.

2) Looks like it’s pineconing, the scales are raised. If this is confirmed, it’s bad news, there’s no cure for it.