Informations about my tank: Size: 5 gallons Filter: Aqua tech 5-15 Heater: Tetra 50 watts Cycle: Yes, fishless cycled for 2 months Ammonia: 0 ppm Nitrite: 0 ppm Nitrate: 30 ppm Ph: 7.6 (the maximum of the color chart)I added my betta 2 weeks ago. Here's a picture of when I got him:View attachment 199408 During his first week, I watched the parameters closely and everything was fine. At the end of the week, he looked like this: View attachment 199409 But now, he looks like this: All the plants inside the tank are kind of plastics, but I checked everyone of them to make sure they didn't have anything sharp and they bended well. I'm scared it might be that, he he's been hiding in them since the very first day and it appeared only today, 2 weeks later... I am thinking that it is either the plants, fin rot, or the sudden heat we had in my area. I unplugged his heater when I got him because it was already 30'C in the appartment, and a few times during the first week it went up to 33'C in the tank! I tried using a frozen water bottle, but I think all these temperature changes might have caused stress... The bottle could lower the temperature of one or 2 degrees at a time only. It was hard to control as it was also 36'C in the appartment at those moments. I think it could be the filter's strenght, I always make sure it is at the lowest but sometimes just a little hit is enough to lower the tube quite a bit. I still haven't found a solution to this. What do you guys think? Should I buy a product or should I wait and see if it heals or get worse?