Fin rot: causes and treatment options

[Lilacora]

I've got a male Halfmoon Twintail Betta named Craig - he's my first fish and I've only had him for three days now. I set up a 10 gallon tank with all the essentials - heater, filter, and plenty of decorations and hiding spots. Craig's color was great when I first got him - his body's this beautiful dark blue, and his tail's a vibrant red. But yesterday, I noticed his face is losing some of its color and turning white, and there's this small dark patch at the end of his tail. Being a newbie, I immediately started researching online. From what I've read, it seems like the discoloration could be due to stress and should clear up in a few days. Still, I'm worried it might be some kind of disease, especially with that dark spot on his tail. Can anyone help me figure out what's going on? I'm really attached to Craig already, and I want to make sure I'm taking good care of him. I'll post a picture of him for reference.

[earthie_9]

I don't think it's fin rot - the dark edge on his fin is pretty common in bettas, and it usually fades as they get older. I'm more worried about the color change on his head, though - that's not something you hear about often. I'm guessing it's stress-related, like a lot of issues are.

Are there any other fish in the tank with Craig? It'd be great if you could post a picture of the whole tank, and let us know if he's been eating okay. Since he's new and the tank is new too, I'm thinking the tank might not be fully cycled yet. You should look into the Nitrogen cycle - it's super important for keeping fish healthy. If you can, test the water for ammonia, nitrites, and nitrates, and post the results. What's the temperature in the tank?

For now, a good first step would be to do a big water change - try changing out around 50% of the water.

[Lilacora]

There are no other fish in the tank with Craig. I didn't get a chance to cycle the tank before introducing him, as he was initially in a temporary half-gallon tank with no heater or filter, and I wanted to get him into a better environment ASAP. The tank temperature is stable at 78°F. I haven't had the chance to purchase a water testing kit yet, due to being a bit short on funds at the moment. Some people on another forum have told me that since I've conditioned and cleaned the water properly, the tank should be fine, but I'm still a bit concerned. This morning, I noticed that the discoloration on Craig's head has developed into light pinkish-red streaks. Unfortunately, I won't be home all day, so I'll take some pictures of his head this evening and post them for your reference. However, I can post a picture of the tank for now. I'm aware that the plastic plants aren't ideal, and I'm working on ordering some real plants to replace them as soon as possible.