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Oil film on water surface

Dr. White

Dr. White

Member
Joined
26 Jul 2023
Messages
73
Location
Swindon
I've been having problems with an oily film on the water surface which I've been regularly draining off. What is quite strange is that I have a lily pipe set, so the water is continually 'skimmed' yet that isn't helping. My thoughts are that the oil must go right through the external canister filter and is being spat out again to float to the surface. I recently cleaned the filter media, hoping that might help, but it didn't.

Aside from that, the tank has been running for about 2-3 months and is very healthy, nutrient levels are extremely low and plants and fish thriving. Stocking levels are low. The fish are never overfed and there is no uneaten food lying around for more than a few minutes, and there are no fish or inverts missing, so no dead bodies, so I don't know where the oil could be coming from.

Has anyone else experienced anything like it and found the cause?
 
Dr. White said:
so I don't know where the oil could be coming from.

Has anyone else experienced anything like it and found the cause?
Click to expand...

A lot of people experienced it...

Could be from the plants... Plants can excrete proteins and essential oils from their leaves during their metabolism and this can create oily and or even foamy surface debris. I'm not sure if we know the main cause of why plants do this and it can come and go away again on its own devices. It could be several things, the amount of plants x surface space x water volume x fertilisation. In most aquariums especially if densely planted and even more if CO² is added we can't speak of a natural equilibrium in the amount of relatively fast-growing plants and amount of secretion vs. the relatively small water volume it is in than it adds up and collects.

The mystery is that it can stop all of a sudden and go away again without changing anything in your husbandry scheme... Something is going on triggering the plants to suddenly release an extra amount of oils etc. The cause remains the question I'm not sure we know the answer to. I don't know it and never found an answer other than it will go away again. And that's also my experience. I experienced it several times in my previous high-energy aquarium as if it had some kind of natural cycle. I guess it's in the most unnatural thing we all have, the amount of plants x the volume.
 
If the "oily film" keeps coming back I'd expect it is biofilm rather than actual oil, that is, it is growing back which is why you can't find the source of it and why you can't keep on top of it manually. That being the case you'll need either a proper skimmer (which will remove the biofilm) or an airstone (which will disrupt the biofilm) to sort it out.
 
Andy Pierce said:
I'd expect it is biofilm rather than actual oil
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Yes, it's a combination of oils proteins and bacteria feasting on it... :)

I believe Diana Walstad wrote about it in her book, but I don't know all the details because I never did read all of it. I also remember an interview where she discussed why she revised the never-water change concept in her second edition. It was because of the possibility if present harmful pathogens collecting and living in this surface film such as Mycobacterium marinum. Most bacteria also secret oils and have oily skin.

Algae and plants can produce essential oils, that is what their smell is made of... Whit aquatic plants you don't smell as long as they are submerged... Handel them in the air and you'll smell them... Some rotalas have a relatively strong smell to them if you rub their leaves it comes out. Same as Basil, rub your hand through the leaves and it starts to smell 3 times as much then releases a lot of volatile and smelling oils.
 
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Hi all,
Dr. White said:
Aside from that, the tank has been running for about 2-3 months and is very healthy, nutrient levels are extremely low and plants and fish thriving.
Click to expand...
That is the main thing.
zozo said:
Could be from the plants... Plants can excrete proteins and essential oils from their leaves during their metabolism and this can create oily and or even foamy surface debris.
Click to expand...
_Maq_ said:
Try feeding different food.
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They do, and food is often a source of oils.
zozo said:
I also remember an interview where she discussed why she revised the never-water change concept in her second edition. It was because of the possibility if present harmful pathogens collecting and living in this surface film such as Mycobacterium marinum.
Click to expand...
Which brings us on to @Dr. White how much water do you change every week?

cheers Darrel
 
dw1305 said:
Hi all,

That is the main thing.


They do, and food is often a source of oils.

Which brings us on to @Dr. White how much water do you change every week?

cheers Darrel
Click to expand...
I was changing about 20% a week, but in the last 3 weeks or so with the oily film problem, I'm probably changing around 2-5% a day as I draw off the film so I've not been doing weekly changes.

I was wondering if the spirulina wafers that I had been putting in for the ottos and shrimp and leaving for quite some time was a source, so I stopped a while back. But that didn't do it. Aside from that, I feed pellets, granules and flake and surprisingly I'm still getting midge larvae from the garden at this time of year, so the cardinals have been enjoying them regularly. But as I said, I do feed very sparingly and make sure everything gets eaten quickly. Aside from the wafers, that was.
 
Andy Pierce said:
If the "oily film" keeps coming back I'd expect it is biofilm rather than actual oil, that is, it is growing back which is why you can't find the source of it and why you can't keep on top of it manually. That being the case you'll need either a proper skimmer (which will remove the biofilm) or an airstone (which will disrupt the biofilm) to sort it out.
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Airstone sounds like it would be worth a try, thank you. I'm a little annoyed I didn't get that sorted sooner, as I am off on holiday for a couple of weeks tomorrow and don't have time. I am expecting to return to a really horrible slick - but my major worry about that is that it will reduce light getting to the plants.
 
I had a strange one recently.

I pointed all my spray bars (which are underwater) at the surface to increase surface agitation. This decreased the flow in the main tank too much, and I found that a film on the surface appeared. I then moved the spray bars down a little (increasing the flow), and the film disappeared. I'm not quite sure if this is expected (or whether it was something temporary), but is this expected or make sense?
 
I tend to get this on mine too. I run an Oase skimmer, which keeps it pretty much crystal clear most of the time. I'd recommend it, although others shout Eheim etc which I'm sure are also good. The sponge needs cleaning two or three times a week but it's a two minute job.
 
Karacticus said:
I tend to get this on mine too. I run an Oase skimmer, which keeps it pretty much crystal clear most of the time. I'd recommend it, although others shout Eheim etc which I'm sure are also good.
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I am running a pair of Oase Biomaster 250s already. Been OK for me, but some just don't like them! The flow leaves the buyer lacking in some cases,

Karacticus said:
The sponge needs cleaning two or three times a week but it's a two minute job.
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I assume you mean the pre-filter? That is quite surprising to me. Whether running one or two canisters, I only needed to clean the pre-filter once per week. I suspect you have some heavy loading in your tank?
 
BRJP1 said:
I am running a pair of Oase Biomaster 250s already. Been OK for me, but some just don't like them! The flow leaves the buyer lacking in some cases,


I assume you mean the pre-filter? That is quite surprising to me. Whether running one or two canisters, I only needed to clean the pre-filter once per week. I suspect you have some heavy loading in your tank?
Click to expand...
Oase surface skimmer, not canister. I also run an Oase canister filter but it defintely takes me longer than two minutes to clean the pre-filter! 😅
 
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