You can’t really do anything to be honest. You can educate the owner and they are the ones who can do something for them. So many things can cause them to die. Too much ammonia or nitrite, the small fish bowl, incorrect temp (no heater) and no filter can cause disease. So unless the owner is willing to provide all of those things you really can’t do much. SorryHello. I have never owned a fish in my life and I don’t know anything about them. I am babysitting 2 Bettas for my mother in law who is out of town for 3 weeks. One of them already died on me and I feel horrible. Now the second one is acting like the first one did before it died. Here’s the rundown. She brought them to my house in small fish bowls- no heater, no filter. They eat pellets and she told me 4 pellets 2x a day. They have been with me for 2 weeks and I have already changed the water 3 times and used water conditioner she gave me. The first one died after a week at my house. The second one was looking good and happy but 2 days ago he stopped eating, and is acting lethargic- barely swimming- just hangs out at the top of the water. I have been doing research and I think it’s the water temp. But I have no way of heating this tiny fish bowl. I put Luke warm water in but it gets cold quick. I’m tempted to take him home to his big tank w a heater and filter that she usually keeps them in, but I don’t know if another change in water is going to shock his system and kill him. I don’t even know if her tank at home is still on or if she unplugged it all while she’s gone. Any advice??