I have a water skim or slick on my 5 gallon tank. I have no clue what it is or came from. My filter exit is creating bubbles that won't go away and along the edges of the tank in the half where the filter is located. I have a Tetra in tank filter. The filter clogs rather fast when replaced. I don't have a test kit. Also had a rather large fish loss after putting 2 new fish into the tank including the new ones. Not the first time. I was manage to save 1 guppy and my Albino Cory Cat. I am going to be getting a bigger tank as soon as I can along with better filtration and UV sterileizer.