Icky small brown spots on inside of aquarium - please help

Hi - we have a 10 gallon aquarium w/3 mickey mouse fish, 2 glass fish, an little eel, and 2 blue shiny fish. We had 2 snails but a few days ago they died - kind of came out thier shells and oozed slimy white stuff. Cleaned the tank and put in new water - to 25% of tank - changed filter etc. This week we have small icky brown spots on inside of tank - we are new to fish tank things have no clue what it is or what to do. Fish seem ok so far but I am thinking this is not good to have - PLEASE HELP.

 

Some info on brown algae