Loaches Online Forum

This is a recent development in a tank that has seen no significant changes in several years. It is a planted 75 gal w/ 3 clowns and 3 albino plecos, one bank of T5 lighting. In the last 3 weeks or so there's been a protein? oily? unknown?? film on the surface of the water, not thick by any means, but noticeable. I thought maybe I got something in there from my skin, but I found a way to skim it during my water change yesterday, and it was pretty much gone, yet today I can see it's starting to collect again. So, it seems to be coming from something in the tank. Without going into detail about my rather typical tank, suffice to say, nothing to my knowledge has really changed recently- so knowing that, what would you guess as possible causes for an out-of-the-blue surface film on your water?

It may be from protien & oils in the foods you're feeding. If that's all it is, increasing the surface water movement will help. Are there lots of floating or very tall plants, that can decrease the current as well.

I had the same problem a while back. I got a surface skimmer for my filter intake. It was less than ten bucks I think. 'Did the trick.

there is plenty of stuff living in our tank's neuston. It comes and goes and helps regulating the bio-chemical processes in our tanks... or contains algae, and/or good bacteria...

http://en.wikipedia.org/wiki/Neuston

The oil-coloured schlieren (cords) for example could be from bacteria eating the chelators of iron fertilizer (or so...).

German links for pictures:

http://www.aquamax.de/HG27UG02.htm

http://www.aquamax.de/HG27.htm

here in nature:

http://www.aquamax.de/HG27UG01.htm

the linked article explains, once you break the film with your fingertipp it stays broken, oil-films would re-join.

A bio filter may give some inhabitants of the surface film a more desirable home and some may move. I occasionally had some suface film, but now did not occure any more for a long time, actually it disappeard last after adding a larger tank. Once I even had a tight diatomen (brown algae) film - that was too tight and grew fast. Other than that I never worried about my surface film, but kept an eye on it.
It indicates that there is food for micro organisims available in the water, perhaps waterchanges reduce the nutrition source.

hm, interesting stuff. although i can't read german, i do not have anything like what i see in those pictures. it is not oil, because it does break apart and stays that way, so that's good to know. who wants an oil slick on their aquarium ?! anyway, i guess my main two concerns were that it was something that would 'smell' bad to (or be bad for) the fishes (although they do not seem to be affected at all) and/or that it would cut down on the light reaching the plants. i do add stuff every water change (10 gals, once a week), namely Instant Amazon, Aquarium Vital, Blackwater extract and a complete multi-nutrient w/ iron and iodine, but I add these things at half (or less) the recommended amount... and as I indicated before, I've been doing that for years... however since you mentioned "iron", i will say that my plants have been looking less than robust lately and it's entirely possible i've been inadvertantly overcompensating with the plant fertilizer.
I have an ehiem cannister, and i think they have a skimmer attachment so i'll look for that...
thanks for all the replies! happy fish watching...

check that on the skimmer attachment- eheim's is a surface skimmer, not a protein skimmer, and from a quick search on the topic, this is not a trivial difference. i'm not too sure it will work for me.