# Slimy film on top of Water



## Bill Weber (Jul 17, 2005)

After having a planted tank for several years I thought I have seen a little of everything BUT....

I have been getting a scumy film on top of my water every day for the last couple of weeks. I syphon it off during water changes but it keeps coming back. I use RO water changing every 3 days. My fish load is 6 medium Discus and several corys in a 70 gallon tank. I am injecting CO2 and keep my ph at 6.5. I just started dosing potassium and plantex CSM for the plants. The problem is not clearing up.

Any ideas would be helpful.


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## 247Plants (Mar 23, 2006)

I believe its a protein build up that causes that...

Mollies and such will eat it...agitating the surface seems to help....and if all else fails lay some paper towels on it and it will pick it up...


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## trenac (Jul 16, 2004)

It's not harmful just ugly!... I like using a surface skimmer to keep my water surface free if scum.

A little info... http://www.skepticalaquarist.com/docs/biofilm/surscum.shtml


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## Salt (Apr 5, 2005)

This question comes up often, and almost always the first reply suggests clearing it with paper towles.

While this will clear it, the film is an indicator of a deeper issue that paper towels aren't going to fix.

I believe it's caused by a buildup of organic by products and low dissolved oxygen.

It should clear up by running aeration. You can put it on a timer and run it at night.

I personally believe that this is adequate for open top tanks, but not for closed top tanks, which (again, my personal belief) should have aeration running all the time. I have found that you don't lose much CO2 at all with aeration running in closed top tanks. With a pressurized system, turn it up slightly to compensate.


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## Yzfr6 (Apr 28, 2006)

I agree with Salt. I added a pump for airation and the problem went away in my 125 gallon tank.


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## erijnal (Apr 5, 2006)

If you have a canister filter, point the output upwards at a slight angle to ripple the water a little. A pump/powerhead angled the same way will do also. That should clear up your problem. I guess it's related to the aeration that Salt mentioned.


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## John N. (Dec 11, 2005)

Is it really aeration or simply surface aggitation that stirs the "slim" build up back into the body of water? Either way aeration or angling up the spray bar for surface aggitation will help reduce the slim build up. Feeding less also has an effect.

-John N.


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## 247Plants (Mar 23, 2006)

> This question comes up often, and almost always the first reply suggests clearing it with paper towles.
> 
> While this will clear it, the film is an indicator of a deeper issue that paper towels aren't going to fix.


I dont believe there is a "fix" for this film........Its a naturally occuring biological process

The best explanation that Ive heard is that its protein lipids that coagulate on the surface as they are lighter than water. From the fish we put in there to the food we feed them, it all contains protein lipids which contribute to the surface film. I believe paper towels will effectively skim the surface enough to remove the majority of the film. Im perfectly ok with using surface agitation to circulate the film until it breaks down enough to decompose too. But just for the sake of information, if everybody had low surface agitation, even those that are fish only, it would result in surface film....


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## erijnal (Apr 5, 2006)

By the way, this may or may not be related, but I recently added a lot more plant mass to my ten gallon, and the surface film is gone now.


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## Bill Weber (Jul 17, 2005)

All,

Thank you so much for all of your comments and advise. I do run an air stone at night which clears the film by morning only to watch it cogulate back to its original volume by night fall. I was concerned that switching to RO Water might have had some underlying impact on this situation. I will look for what is right with my tank and overlook this blemish.

Thanks again.


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## djlen (Jun 22, 2004)

This has occurred a few times for me as well and most of the above remedies will work.
I once described that problem to an old friend who's opinion I respect a lot and he asked if I was injecting CO2. I said I was at about 30ppm and he suggested I bring it down to about 20 - 22ppm. I thought that it sounded a bit wacky, but tried it and within days the 'slick' was gone. I still can't explain why, but it's worked over the years every time I had that problem.
Ofcourse it's really academic if you don't inject, huh? 

Len


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