Okay, so here is the deal. NOBODY can seem to agree how drastic and how often water changes should be and that's just the truth. All sorts of "experienced" people are all saying different things, all with good reasoning.
Today I noticed an oily looking sheen on the surface of the water in my 1.7 unfiltered tank. Currently I do a fifty percent water change once a week and scrub everything in the tank because I wanted to get a feel for when the water needs to be changed since I can't get a definitive answer. There seems to be a slight sheen on the surface most of the time, so my instinct is not to be worried since his water change day is tomorrow (but just in case I wanted some second opinions).
Is this normal? Does this happen to anyone else? Is this an indication that I need to be doing more water changes? Let me know what you guys think :)