White mold and betta fin rot

[lalalameg]

I recently moved my betta to a 2.5g tank with a small filter, and he was doing great (actually a lot better than when he was in his bowl, his fins were healing from previous fin rot) and the other day I happened to look in his tank and his fins were as ripped and jagged as ever, even worse than when he was in his bowl. I figure he was getting picky about the water as I hadn't changed it in a little over a week, and when I went to change it today I saw the filter had molded. I wish I had taken a picture of it, but it was white and all over it. Not the fuzzy kind of mold but in little "bean" shapes, is the best I can describe it. I'm assuming that was the cause of his suddenly torn fins but I would still like to know what it may have been so as to prevent it in the future. Thanks!

 

[lalalameg]

Planaria!?

Upon further research, I think I may have planaria on my hands. The only thing is is that I do not overfeed my betta, his tank is next to my bed and I feed him before I go to sleep so I see him eat all of his food. I am also feeding him freeze-dried bloodworms if that could be helpful information.