Oily substance on water surface (poly tank)

[HumanBean]

I did regular maintenance on canister filter on my poly tank. Not the first time and fiter is an old filter. I am seeing an oily surface with vasline like stuff . which I manually skimmed twice . not too sure what it is.

Not from food because I feed massivore and tilapia and its vet eaten in 10 min.

This layer was not there before this maintenance. Just wondering what it is and is it harmfull to fish ?

 

[D7620]

Put a paper towel on top of the surface, it'll absorb all of it up

 

[framcosco]

Tilapia has oils and will create that oily surface unless you have a skimmer/sump.

 

[predatorkeeper87]

I get the same thing on my poly tank, and as fram said, its most likely from the tilapia. I feed my polys a good portion of it every day and I always have that film on the surface of the water.

 

[isde02]

X3 oil in tilapia also fish oil is added to pellet foods. I had it on the surface in my tank also, I just aimed the return from my canister at the surface and it eventually went down the overflow.

 

[Jimmythefishkid]

It also could have been from the excess of oils on your skin while you were doing maintenance

 

[HumanBean]

It also could have been from the excess of oils on your skin while you were doing maintenance

It can't be. fish oil idea make more sense.

 

[OTp1144]

it's biofilm. you need to increase your surface agitation and it'll go away

 

[RD.]

All food that contains marine proteins such as fish, including the vast majority of pellet feed, contains fatty acids and amino acids that can both contribute to surface scum.

 

[rodger]

Unless you have something that skims the surface, you will have scum. My tanks with overflows don't have it. Nothing you do will prevent it. You can buy surface extractors for some filters that will collect it.