There hasn't been any temp change & unfortunatly I work away from home (wont be back home for another 2 weeks) so I have not had the chance to do any levels since the yellow film appeared,its about 12"x6" right in the front & centre of the tank ,if its still there when I get home I'll post some pics,it litteraly appeared over night, does it matter which way the water flows through a uv ,I would have thought not but hey,maybe ,I just had a look at the web site selling the uv and it shows the water flow going one way but I have hooked it up the other way ,hmmm ,what do you think ?