Ive had this little betta fish for 3 weeks now. He hasnt been eating and kind of lazy, I thought he was just adjusting to his new home. Ive tried the pellets, blood worms, and baby brine shrimp, all with no luck.. But today I noticed a long white stringy thing coming out of his anus. Maybe a worm? And his tummy is swollen, it looks like he's constipated. The rest of his body is fine, no pinecone look to him. He is in a filtered 2.5 gal tank (till I can upgrade) with no tankmates. I originally got 2 fish because petco said I could put them both in there with a divider, and after 2 days and some research, I got a 3.5 gal for the other, bigger fish. He seems to be doing really well though. They also told me these guys were very minimul effort, which isn't the case so far. I'm willing to put in the work I just don't know where to start.