Surface film

>Date: Tue, 21 May 1996 14:15:30 PDT
>Subject: Re: Surface Film
>> From: svr at eecs_umich.edu (Steve Robertson)
>> First, to Mark McClean:
<snip> but every day a slick clear film forms all over the surface of the
>> >tank.  The pH is 6.8 and the water is soft.  I have been skimming it off,
>> >but every day it returns.  Is this related to having plants ?  I have never
>> >had this problem in any other tank and at a loss as to what to do.  I would
>> >appreciate any help.
>> >
<snip> I suspect the Mollies are responsible for clearing the surface,
>> since I see them "skimming" the surface as if they are eating something.  I
>> don't think they are gasping for air, because they aren't breathing hard -
>> they really appear to be grazing at the surface.
>I have similar surface film which seems to be strongly related to the
>amount and type of food I'm feeding. (I'm feeding some Bettas for breeding
>and they get lots of fresh or frozen brine shrimp).<snip>

Steve, Mark and Stephen,

I had this film on my tank for months. Several people on the list suggested
iron as a cause and I now believe that to be true. The film on my tank has
recently gone away. I have Terralit in my gravel which contains iron and I
added rather too much Tropica Master Grow during the initial set up of my
tank. I have cut way back on the fertilizer and kept monitoring my iron
levels. Now that the iron is down to about .1 the film has disappeared and
the thread algae has also almost disappeared. I feed plankton and
bloodworms, flakes and shrimp pellets and I haven't made any feed changes
so I don't think it can be anything to do with feeding. I doubt if Mollies
would eat the film -- but who knows -- maybe, but I suspect the film's
disappearance had to do with the other changes mentioned. I think if you
have a greenish-white film on the surface of your tank that your iron
levels are too high.

Anyone else have any thoughts on this?

in Vancouver where it's wet today.