thin film on the top of the water? what is it?

chee

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Jan 6, 2010
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so when i look at the top of my water through my tank (looking up) there is a very thin film that is very faintly rainbow-ish kind of like oil but not really. i once read that you can use a piece of paper to clean the top of your water and have tried this with moderate success.

does anyone know what this is? what causes it? i use a water conditioner so could this be the remnants of it? (i do regular 25-30% water changes)

thank you
 
Its called slime, an oily slick and byproduct of decaying organic matter (fish food, dead leaves, fish poop). Use a surface skimmer to remove it.
 
i have that same problem in my planted angel/discus tank. It doesnt seem to bother the fish at all, it it goes away when i do water changes
 
try to angle your filter to beak the suface of the water this will help to beak it up so your filter can remove it . another way is to use a jug when doing a wc and just tank the water off the surface
 
Yeah, it's mostly protein scum. You could try a surface skimmer or adding a powerhead at the surface, that would help. I don't think it bothers the fish but I imagine it limits the gas exchange of the water, which is why having more surface disruption would be helpful.

I find I get this scum especially on my tanks where I feed few vegetable/algae based foods, more protein rich meaty foods, for example my tetra tank. Goldfish tanks and platy tanks, not so much...which is why it makes me think it's protein that is the culprit.

And yep, it's oily for sure...hence the rainbow effect
 
I have a surface skimmer built into my intake on my C-160. It custom built with two inlets, one down deep in the tank, the other at the top. both meet at a T junction and then head into the filter. Its very effective lemme tell you. minimal CO2 losses.

I built it out of 1/2: PVC, lemme know if you want the plans.
 
The scum also contains biofilm, which helps with your nitrogen cycle. I let it be. My shrimp spend all day at the top of the tank eating it.
 
I built it out of 1/2: PVC, lemme know if you want the plans.

that would be great! i think i have a picture in my head of what you are talking about and it really makes sense. would be very interesting to see how you made it, plus i love building stuff myself.

thanks
 
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