During the last few months I had a thick bacteria film on the watersurface of my tank . On the one hand it does not look appetizing, it prevents the water to exhcange gas and lowers the power of the LED light. Checking the parameters of phophate and nitrate didnt bring any abnormailty. A biological removal by adjusting some parameters wasn’t needed now. So I started the mechanical removal during the water change over several weeks ny vacuuming the water surface of my tank. This was not successful 🙂 because the bacteria came back very fast within a few hours.
During my reserach on the web I discovered the Eheim Skim 350 and ordered him immediately. Today, after having this little pump for some weeks, I’ still very happy with it. The water surface is uncovered of bacteria. The small Skim 350 uses only 5 watts, it helps promote the exchange of gases in the aquarium and can be postioned elegantly in a corner or behind a reef pillar.
More information:
https://www.eheim.com/de_DE/produkte/zubehoer/reinigung/oberflaechenabsauger_skim350 
1 comment on “Helpfully against bacteria films on the water surface: Eheim Skim 350”