# oily film on top of water



## tom g

does anyone know what would cause an oily film on top of the water my tank has been running for a three months and for some reason it looks like there is a film of oil on the surface the fish are happy , but when i compare it to my other tank it just doesnt seem right i am running a marineland hob filter i have a air bubbler in the tank 
thanks 
tom


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## Darkblade48

The film of oil is perfectly normal, if unsightly. 

It is usually due to protein content from the fish food, etc. If you reduce your feeding amounts, create more surface agitation or manually remove the scum (either manually or with a surface skimmer), you will be able to remove the film.


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## Mr Fishies

On my tanks it seems to come and go. I've not found anything that correlates to it since my food regimen doesn't really change. There are natural oils, proteins, bacteria, dust all accumulating on the surface of your tank all the time.

Unless for you, seeing it is like being stabbed in the eye with a pin, live with it...seriously, you'll drive yourself nuts trying to get rid of it unless you go to the hassle and expense to get a skimmer, and then you have a skimmer in your tank...and I think you can't run one on a HOB without DIYing something that would probably look a lot more Fugly in your tank than the surface scum.

I've seen posts on PT or some forum where a hobbyist tore a tank down, bleach dipped plants, washed gravel, disinfected the tank...just to get rid of surface scum. Within days it was back. (Right now, I'm holding my fingers in a "L" shape on my forehead thinking of that guy ).

In this hobby, we're subject to the whims of nature, sometimes we can direct things a bit, but don't fight it, you won't win.


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## tom g

thank you for the advice , im good to go with living with it , as both tanks are doing well and each one has its own personality ,and to boot the fish are happy so why mess with whats good 
thanks again 
tom


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## Mr Fishies

tom g said:


> thank you for the advice , im good to go with living with it , as both tanks are doing well and each one has its own personality ,and to boot the fish are happy so why mess with whats good
> thanks again
> tom


NP. My snails love it too...much of their time is spent hanging upside down under the surface or around the edges of the tank and leaves at the surface gobbling the stuff up like crazy...well fast for a snail at least.


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## ameekplec.

If you really hate it, I think most of the major filter makers make a surface skimming attachment. I bought the Aquaclear one for $10, and it does a pretty decent job of keeping the surface clean.


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## Cory

Hmm, only time I've ever had this problem was tanks that had stagnant water. It has always gone away once I corrected the surface agitation problem though. A protein skimmer for fw is excessive. Try ensuring that the entire surface of the water is moving and when you do your h20 changes let the water fall into the tank from a few inches up so it will agitate it further. I've never let it hang around long enough to know if it's detrimental or not. I would think a lot of the film would hinder osmosis and prevent as much o2 from getting into the water column but if these guys say it hasn't been a problem for them I'd take their word.


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## ameekplec.

A protein skimmer isn't nearly as effective on FW as on SW - it's pretty much a waste of money. 

All you want to do with the surface skimmer is to mix the surface proteins back into the water to be removed by your filtration. The surface film will hinder diffusion of O2 into the water, but as long as you agitate at least part of the water's surface you won't run into dissolved oxygen issues.


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## Calmer

Does the marineland hob filter have the bio-wheel running on it? I thought that the bio-wheel would be able to do something for the protein buildup at the surface. You can also lay a clean paper on the surface and then lift the paper out with the protein buildup on it. It is a labour intensive method but it does works. 
I get protein buildup at the surface when feeding frozen and freeze dried food. Mainly with frozen blood worms for my puffers. I use a home made surface skimmer from parts I had lying around.


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## Mr Fishies

ameekplec. said:


> If you really hate it, I think most of the major filter makers make a surface skimming attachment. I bought the Aquaclear one for $10, and it does a pretty decent job of keeping the surface clean.


I forgot about those things completely...but seeing one, I still stand by my original thought that a film looks "better" than one of those hanging off the intake of a filter.  I'm just anti equipment I guess...

I've had a film so thick you could have called it skin and never had fish gasping for air. That's on a tank with pressurized CO2 and canister filters with outputs below the surface too.

Even without the airstone, his HOB will be agitating the surface enough I expect unless it's got some real smooth outflow and the level is just right. I'm not 100% familiar with Marineland HOB filters, I know what the box looks like, that's about it.


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## Cory

Mr Fishies, if your tank is planted which I assume it is if you're using CO2 the plants are releasing oxygen into the water while the lights are on so that could be why a really thick layer is not a problem. I think it's probably a situational thing though, everyone's circumstances will differ and it might be a problem for some and not others. It's always been my policy not to let it develop and personally I think that is the best approach. I know natural bodies of water don't have oily surfaces.


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## Mr Fishies

Cory said:


> Mr Fishies, if your tank is planted which I assume it is if you're using CO2 the plants are releasing oxygen into the water while the lights are on so that could be why a really thick layer is not a problem


Don't think so...I don't have a solenoid hooked up for my CO2 (yet) and run it 24 hrs a day. I run my lights from 12h00 - 22h00. That means 14 hrs a day (or more if you look at the fact plants close up by 21h00 and photosynthesis takes time to start) my plants are not releasing O2 and CO2 is still running. By that logic my fish should be dead, yet I've never personally seen it happen nor read on the web a single case of someone suffocating their fish being attributed to a film.

That said, I'm always ready to learn and willing to be corrected given proof and/or evidence.


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## Cory

They'd have enough dissolved oxygen to last them the night though so you'd never really know for sure. For them to actually suffocate you'd need a complete lack of o2. The conditions could become more anaerobic in the evening but not enough to be a problem. I assume there are areas where you have water exchange in the tank so the o2 level would never hit 0. The only way to test it would be with advanced equipment. I'd say that logic dictates that any barrier to the diffusion of oxygen into the water would hinder that process. Whether or not it can do so enough to become a threat to the life in a tank would require a lot of testing with a lot of different variables to consider.


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## BillD

You can remove it during water changers by using a gravel vac inverted so it sucks from the surface, basically skimming it. Takes a few minutes to get the hang of it, as you want to create a current to the mouth of the vac, but it works very well.


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## ameekplec.

Mr Fishies said:


> Don't think so...I don't have a solenoid hooked up for my CO2 (yet) and run it 24 hrs a day. I run my lights from 12h00 - 22h00. That means 14 hrs a day (or more if you look at the fact plants close up by 21h00 and photosynthesis takes time to start) my plants are not releasing O2 and CO2 is still running. By that logic my fish should be dead, yet I've never personally seen it happen nor read on the web a single case of someone suffocating their fish being attributed to a film.
> 
> That said, I'm always ready to learn and willing to be corrected given proof and/or evidence.


You can get suffocation from not enough surface agitation and a densely planted tank. Both my 20g and 75g have gone through at least one or two episodes, where after a top up, I filled the tanks above the spray bar, greatly reducing or eliminating the surface agitation, and the film took over on top. 
Over the evening when the lights turn off, and the plants begin to respire, it eventually drops the O2 levels down low enough that things start to suffocate - when all your shrimp (even the tiny 2 -3 mm) ones are at the surface, as with the snails and all the fish are pale grey and at the surface, they're suffocating - if I hadn't noticed before I left for the day around 7:30am (lights on at 2 pm), I'm sure I would have lost both tanks.


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## Mr Fishies

TomG, since it seems I may be the only one who thinks you're not likely to get into any problems, don't take my word for it.

Since you don't know if it's oil from your food, natural proteins building up, decaying organics, Eisen bacteria, algae pond scum or who knows what...it's pretty hard to make any suggestions as to how to stop/prevent it.

So, it seems your only choice is manual removal. You can get one of the skimmers suggested (which doesn't really remove it, only sucks it through your filter where hopefully it will be cleaned up), you can drag paper towels over the surface of your tank, carefully suck the film off during regular water changes, raise your filter so the outflow disturbs the surface, what ever other method you choose.

Good luck.


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## Mr Fishies

ameekplec. said:


> Over the evening when the lights turn off, and the plants begin to respire, it eventually drops the O2 levels down low enough that things start to suffocate - when all your shrimp (even the tiny 2 -3 mm) ones are at the surface, as with the snails and all the fish are pale grey and at the surface, they're suffocating


Ameek, I don't want to argue with you on this one. I value your insight and the experience you share with the forum, but I find this a bit tough to understand.

From what I recall of how you keep your tanks you always have a ton of flow and filtration, no? If you have a 75G tank with 2 filters (2217?) or a filter and 1 or more power heads constantly stirring the water, even below the water line, there couldn't be any significant stratification of water happening so I just can't imagine the O2 concentration being any better at the surface than down low. You saw what you saw, saved your fish thankfully but I still have a hard time filing that solely under effects of surface film.

@ TomG: Either these folks all get some freakishly nasty industrial strength surface film with a monstrous amount of O2 sapping bacteria in it, or I am just lucky. I never recommend leaving the health of pets to luck, so again good luck with whatever method you choose to combat it.


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## ameekplec.

The 75g did have two 2217s, but both spraybars are pointed in such a way to maximize flow within the lower parts of the aquarium, but also provide maximal surface agitation - usually they're above the waterline pointing into the water - so when the water level rose above them, the surface agitation was non-existent and the film across the top was allowed to reform.

But it's entirely possible also that the effects caused were independent of surface film, but primarily mediated by plant respiration in the darkness. Although, it was clearly evident that without surface agitation (but with good flow within the water column) DO levels can and will drop dramatically if O2 is used up quickly enough - clearly in this case surface diffusion of O2 wasn't sufficient to keep up with the demand, although the result may have differed in a non-planted tank of a lower temperature (tank temp is 84) with less bioload.


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## Mr Fishies

ameekplec. said:


> ...although the result may have differed in a non-planted tank of a lower temperature (tank temp is 84) with less bioload.


84F (29C), why so high? I keep my tanks about 78-79 (25.5-26C) or so and I thought that was more than needed. You have some special needs fish or just keep it high to ward off Ich or something? Either way, the temp should only account for ~.5 ppm difference in DO. I would put more weight on a high bio-load, since I keep a pretty low load in my tanks and all my outlets are below the water line. I do have a Koralia pointed ~10 degrees up at the bottom of the surface from about 1-1/2 inches below but that's the extent of my surface agitation.

On a related note, I was reading over on TPT someone posted that adding an air stone to tanks with surface film can actually make it worse if it's a bacterial film. It feeds and provides oxygen to the bacteria and the bloom gets worse...go figure.


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## ameekplec.

I keep it high for some plecos from warm water rivers, hence the high flow and high temps. Bioload isn't that high, but it is densely planted.

Figures on the bacterial film - but if it's just surface proteins (partly due to high protein content of food) an airstone would partially solve the problem - although that just pushes the film away.


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## Calmer

I use a sponge pre-filter powerhead with air coming in at the venturi. That way my powerhead adds atmospheric air to the water column. It doesn't take a lot more power than an air pump and stone but it is more efficient. Some air bubbles break the surface but some smaller bubbles are pushed around through the water to enter into the water column faster. The 6 BN plecos seem to enjoy it immensely. The 38 gal. aquarium is planted without co2.

I have been contemplating using two reactors; one with co2 and the other with only air just to see how that works in my 90 gal. http://i301.photobucket.com/albums/nn61/Calmer_2008/Co2Reacternew1.jpg
Less co2 loss at the water's surface due to less surface movement and o2 increase for the fish in the water column. Best of both worlds? Maybe


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## KhuliLoachFan

I would be curious to know if an over-size HOB filter would clear up the oily surface. Since the water flow from my AC110 not only quickly and forcefully breaks up the surface of the water as its overflow drops back into the tank, this might work just as well as the surface skimmer attachment does. In other words, try a bigger HOB filter. 

W


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## characinfan

ameekplec. said:


> Over the evening when the lights turn off, and the plants begin to respire, it eventually drops the O2 levels down low enough that things start to suffocate - when all your shrimp (even the tiny 2 -3 mm) ones are at the surface, as with the snails and all the fish are pale grey and at the surface, they're suffocating - if I hadn't noticed before I left for the day around 7:30am (lights on at 2 pm), I'm sure I would have lost both tanks.


Note: plants are respiring all the time. The dark reaction does not require an absence of light. When there is light, though, plants release more oxygen than carbon dioxide. Everything else is correct.

(Sorry, sometimes I get really anal about plant biology!)


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## characinfan

Another low-cost and low-effort way to get rid of some of that oily scum is to pull a dry cotton cloth (like an old sock or part of an old T-shirt) across the surface of the water. This is what I do when oily scum builds up, and it works.


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## KhuliLoachFan

Re: Cotton cloth to mop up oil slick

I would be worried about getting soap/detergent in my tank.


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## characinfan

KhuliLoachFan said:


> Re: Cotton cloth to mop up oil slick
> 
> I would be worried about getting soap/detergent in my tank.


If the cloth is well-rinsed beforehand, it's not a problem. I keep a stash of "fish cloths," including shredded old towels to spread on the floor when doing water changes. If you're not into doing hand laundry, it's easy enough to wash a load of rags normally, then put them through the machine again without any soap or detergent, just to give them extra rinse cycles.


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## ameekplec.

characinfan said:


> Note: plants are respiring all the time. The dark reaction does not require an absence of light. When there is light, though, plants release more oxygen than carbon dioxide. Everything else is correct.
> 
> (Sorry, sometimes I get really anal about plant biology!)


Bah! An academic answer. Yes, you're technically correct - they do respire all the time.


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## PPulcher

KhuliLoachFan said:


> Re: Cotton cloth to mop up oil slick
> 
> I would be worried about getting soap/detergent in my tank.


I just use a paper towel. Works fine, but you have to toss it out. I chuck them in the redworm bin.


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## tom g

well thank u guys for all the advice let me tell u that i have had no deaths and tank has been running for six months fish are happy , i will get a surface skimer and try that , and i will try to aggitate the water a little better , i have a feelin that my heater is the culprate i am gonna swap it out , i see some air bubbles sticking to the heater not sure if it faulty or crackeed 
thanks 
for the input 
tom


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## oshiet

ameekplec. said:


> If you really hate it, I think most of the major filter makers make a surface skimming attachment. I bought the Aquaclear one for $10, and it does a pretty decent job of keeping the surface clean.


I used this on one of my smaller old tanks with a canister filter. Really helps remove film off the water surface.


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