If that is ick or a fungus - another med that will work is called quick cure. Walmart should have it and it works pretty quick or it did for me.
for a 1.5G, you don;t really need the filter - unless you want some water movement. Also keep an eye out that the bitting does not get fin rot and do not use aquarium salt for more then about 2 weeks. Premix 1 teaspoon per gallon and make sure its disolved before adding the fish