Who Gives A Fish Forums

Hey guys,
I know this might sound weird, but I keep my betta in a 5-liter round bottle - don't judge, lots of breeders do it. My little guy is 2 months old now. The tank's got plenty of plants - mostly frogbit and salvania - and I've also added some Indian almond leaves to the water. Everything was going great, my betta's super active and has grown heaps since I brought him home. But then I noticed this weird white stuff on his dorsal fin. I asked around, thinking it might be some kind of parasite, but people said no. The marks are like little circles with blue in the middle - same color as my betta. They're not holes or anything, just... weird. Anyone have any idea what's going on?

Honestly, the photo's not the best, but I'll give you the benefit of the doubt. I'm not here to judge, but I gotta say, a 10-litre tank or more would be ideal for your betta. I'm really hoping you've got a filter in there, if not, please do yourself (and your betta) a favour and get one ASAP.