Oily Film

[kari]

Isn't this just a normal thing that happens in all SW tanks? Some nutrients build up at the surface if they are not skimmed off by mechanical means like surface overflows. If the surface water of the tank is not drawn off or agitated enough you will get an oily film buildup whether you feed mysis or not.

[untamed]

Yes...I had this same problem on my tank. Basically, the tank itself has become a giant protein skimmer with no collection cup!

For fun, you can stick your arm straight into the middle...go past your elbow...pull your arm straight up and the gunk will coat your arm as you pull it out! Not a solution, but good to gross our your significant other!

You need to draw the water from the surface into a skimmer... or break up the surface with a PH so that a skimmer can get it later. IME, I found it nearly impossible to keep a surface feed working with my HOB skimmer...unless you have perfect evaporation control, the surface will change height and you have a lot of problems.

All that until I got a sump. That solved this problem completely as the overflow into the sump comes off the surface of the tank.

[Bob I]

The Aquaclear idea worked well for me in the past. Right now I have my Fluval return just below the water surface. It breaks up the surface tension just enough to get rid of the film. Just as an aside, in my early fresh water tanks we laid a newspaper page flat on the surface and drew it back to get rid of the film.