# Oily translucent film on the surface of my 30 gallon



## Gizmo (Dec 6, 2010)

As stated, there's a film on the surface of my 30 gallon tank. It's whitish, breaks whenever I stick my hand in or feed, and it's been there for about a week now. Should I be concerned with it? What is causing it? Overfeeding, poor filtration, lack of surface disturbance, or something else?

I feed once a day, a good-sized pinch so enough floats to the bottom for my RCS. My AC50 runs slow due to a prefilter and lack of cleaning (1/3 capacity, by my guestimation), and the water level in the tank is high enough there's no drop from the filter's outlet into the water, so it's just flowing in. There's no other source of surface disturbance either, besides the filter. I had a recent fish fatality 3 days ago which I was not able to autopsy cause it sank to the bottom and the shrimp ate it in under a day (it was a galaxy rasbora).

On another note, my zebra danios flash on a regular basis. My water testing as of yesterday was 0.25 ppm ammonia (which might be it, but might be tap water interferences as well), 0 ppm nitrite, 20 ppm nitrate, 7 degrees KH, 7 degrees GH, 0 copper, 0.5 ppm phosphate, 0.2 ppm iron. The danios seem bloated, but I've been feeding garlic periodically over the past month and they don't have any other symptoms of parasites aside from being fat.

Any and all thoughts are appreciated, thanks


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## jrman83 (Jul 9, 2010)

Normal, unless it is multi-colored. Powerheads will break it up, as will most any kind of surface turbulence.


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## fishkeeper (Jan 3, 2011)

Hi Guy Miller,

this film consists of microorganisms, who profit from being in water and air at the same time. They use the nutrients of the water and the air's oxygen.

You normally have them, when there are many nutrients in the water and/or many fishes.
If the film gets to thick, it can disturb the oxygens way into the water.
There are snails and fishes, who eat this film. Guppies for example like it very much.
And of course, as the other guy explained, You can use turbulance on the water's surface.


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## Kaiden32 (Sep 4, 2010)

Yeah, as I understand it, it is fine unless it is like rainbow colored when the light shines on it. then you have a problem.


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## Gizmo (Dec 6, 2010)

Alright, then I'm not gonna freak out too much. I was worried it was going to inhibit gas exchange on the surface. Not a problem during the day when my plants produce O2, but at night I leave my CO2 on and have a heavy plant load, so I worry about asphyxiating my fish.

Note: The reason I have not invested in a solenoid is because they are expensive (at least from the only place I know where to get them from), and I've heard they're prone to failure due to heat buildup.


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## jrman83 (Jul 9, 2010)

You leave CO2 on at night? Do you use a CO2 controller? I used to leave my on at night, but only did it with a ph controller.


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## Gizmo (Dec 6, 2010)

Yeah, I leave it on. I'm only pumping in about 1 bps, so it's not much.


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## jrman83 (Jul 9, 2010)

No wonder you don't see much pearling. I'd go to at least 2.


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## Gizmo (Dec 6, 2010)

I've tried bumping up the bps and without a solenoid I run the risk of asphyxiating my fish some night when I forget to turn the CO2 off.


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## automatic-hydromatic (Oct 18, 2010)

that's the only reason I have aeration on my 30 gallon; to keep the surface moving and keep the film from occurring


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## saflager (Jan 19, 2011)

I discovered an oily film on my tank surface too that has never been there before. Nothing has changed as far as filtration and water movement. I was wondering what does it mean if the surface is multi-colored? When the light shines on the surface it looks like a prism. Is this ok? How do I get rid of the film, I don't like it.


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## jrman83 (Jul 9, 2010)

It means something is in your water. Could be from something sprayed in the room (air freshner, furniture polish, etc), something you maybe had on your hands, could be just about anything. If you're concerned do a water change.


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