So I've had my Harlequins for about a week now in a 20g planted tank, and all 7 of them have a white dot on their mouth. I guess it's to late to quarantine now if it is a disease. They are healthy, swimming around and always looking for something to eat. I am treating them with Melafix incase it is a fungus of some sort. Here's a picture of one like it Important - White Dot On Harlequin Rasbora's Mouth?