betta fish behavior issues: sudden flaring and attitude changes

[Lynxo]

Hey guys, I'm pretty new here but I had to ask for some help. So, I've had my betta Casper for about a year now, and he's always been such a sweetie - happy, curious, the whole works. We did have a bit of a scare with fin rot when my boyfriend was watching him, but that's all cleared up now and his fins are almost fully grown back. He's super active, which is great, but lately, he's become really aggressive. Every time I go near the tank, he flares up at me and won't follow my finger like he used to - he just zooms away and then comes back to flare some more. I'm worried I've done something wrong. His tank is a nice size, either 3.5 or 4 gallons, and he's got plenty of stuff to keep him occupied - leaf hammocks, a hiding cave, rocks, and a filter. I've also got some live vine leaf plants in there that he loves. The water temp is usually around 79 degrees, and he's got a bubble nest going on at the top of the tank. I try to feed him twice a day, but sometimes it's just once. Did I mess something up and lose my sweet boy?

[infold]

I think it's just one of those things, you know. Fish can be weird sometimes. Maybe something in his environment is stressing him out, like the TV or a sudden change in the room. It's possible he's just going through a phase, but I have to say, the Jaws theory is kinda funny.

[coltin]

Hi and welcome to the forum. It's great to have you on board. Now, let's take a closer look at Casper's behavior. If he's built a bubble nest, that's a clear indication that he's feeling broody - like a mother hen guarding her eggs. This territorial instinct is kicking in, and he's essentially warning you to stay away from his nest.

[Lynxo]

Thanks coltin. That's really helpful to know - I had no idea about the bubblenest being a sign of him feeling broody. I suppose that makes sense, given how protective he's being. However, I'm still a bit concerned that there might be something else going on. You don't think it's possible that there's an underlying issue that's causing him to feel this way, and the territorial thing is just a symptom?

[coltin]

Unless Casper stops eating or shows signs of illness, like weird red or white growths on his body, I'd say he's just feeling a bit grumpy and territorial, like coltin mentioned.