Re: Surface Film

> From: svr at eecs_umich.edu (Steve Robertson)
> First, to Mark McClean:
> >     I am new to planted tanks and am having a problem with my 125 gallon
> >setup.  We are using vermiculite and soil under a gravel substrate.  The
> >tank has been planted for two weeks now.  We are growing plants that do well
> >in low light,  We have 160 watts on 11 hours a day.  Everything is growing
> >fine 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.
> >
> >Mark
> I noticed the same thing in my 29 gallon tank.  A few days ago I added two
> black Mollies and the film dissappeared.  I also added a solution of K2SO4
> and water (a supplement to my Flourish nutrient mix based on the PMDD
> recipe).  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). I don't think it's
related to vermiculite because it happens on my gravel only tank too.
Others have commented on this to the effect that its a bacteria which
is feeding on surplus nutrients (phosphates?). I think its worse if you
have little or no filtration or surface disruption but it's not really
harmful. It's also an indication that you should probably increase the
volume and frequency of water changes esp. if you're feeding lotsa fish
or carniverous fish. Don't panic; its not fatal. Ok panic a little bit
if algaes are taking over your tank and threatening to spill out into
the room and engulf the TV and the chesterfield which might interfere
with you're getting up to get a fresh beer between football/hockey/
basketball/baseball quarters/periods/innings. BTW, my tank with Platys
has less but I attributed that to feeding. Interesting thought.

Steve  Vancouver BC  (if it's not raining, it would like to rain)