# Surface Film



## John Starkey

Hi all,i thought i would post this here instead of in my journal,as i am hoping for more opinions,

Right the only real probs i was having while doing a fish less cycle was a few diatoms/brown algae,now my filter has matured that has cleared up nicely,i was dosing easy carbo 1ml a day and i was getting this surface film so i quit dosing that and things seemed to get better,then i decided to up my co2 rate from 2bps to 4bps as the marsilea was struggling a bit,that improved but so did the surface film,so i am thinking the film is being caused by too much co2, my drop checker is a nice yellowy / green colour,all i dose now is TPN + 2 1/2 ml,s a week

your thoughts  and idea,s what may be causing it would be very helpful 

regards,
john,


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## Mark Evans

oddly enough, me and james have had discussions regards to surface film and co2...but no conclusion. 

It's weird, sometimes i get it, and sometimes i dont.   :? 

when i do have it, it's easy to get rid of, using a plastic container....forget paper towels.


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## John Starkey

Thanks mark for your thoughts,i just use my small fish net to scoop it off the surface,but i may reduce the co2 down to 1bps once the marsilea has spread more,its all i can think of doing to see what affect that has if any,
regards,
john.


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## Themuleous

Yeh me to, some tanks do some don't.  I did notice the other day however that when I overdosed excel in my highlight tank, the film actually went and has since come back.

Odd. If Ceg is right (no reason to doubt he is! ) then this probably just proves that the plants in the tank were deficient of CO2 and where 'leaking'.  Adding the excel gave them what they needed and so they 'healed'

You might find this interesting.

viewtopic.php?f=21&t=13512

Sam


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## viktorlantos

Since i do aeration on my small tank at night i never see any oil film.


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## John Starkey

viktorlantos said:
			
		

> Since i do aeration on my small tank at night i never see any oil film.



Well Viktor funny you should say that,because last night i moved my spray bar up higher to cause more surface movement and i came down looked into the tank and surface film was back ?,i have now reduced the co2 bps back down to 2bps and wait to see if it make,s any difference, 

regards john.


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## stevec

theres a post about this with an explanation from clive
viewtopic.php?f=21&t=13512&p=141160&hilit=surface+scum#p141160


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## Dolly Sprint 16v

Hi all
I had this the other week and the only conclusion I could come up with that there may have been some soap / detergent residue on my hands / arms - I usually rinse my hans / arms prior to going into the water which put an oily film on the water surface. 

Regards
Paul.


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## mlgt

I simply add floating plants like frogbit and eventually once it covered a small area of the tank then the oily film stopped.

However recently I have removed the frogbit as it was totally covering the water surface the oily film has come back. But its very slight.

My nano tank doesnt have a lid and is in the kitchen so possibly its from the atmosphere when cooking?


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## nry

mlgt said:
			
		

> I simply add floating plants like frogbit and eventually once it covered a small area of the tank then the oily film stopped.
> 
> However recently I have removed the frogbit as it was totally covering the water surface the oily film has come back. But its very slight.
> 
> My nano tank doesnt have a lid and is in the kitchen so possibly its from the atmosphere when cooking?



Which backs up my comment on here elsewhere - when my plants reach the surface the film goes, when I trim them lower again it comes back.  Trimmed the rotala about 2 weeks ago and it is just about to hit the surface, once it does then I will see if the film goes again.


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## John Starkey

Thank,s guys for all the reply,s some very interesting points there,the film i am getting is like a clear white film and when you pull your finger through it  it clots just like cold white fat does on water,but bare in mind it is a very thin film,

regards,
john.


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## Anonymous

Follow ceg's advice here: viewtopic.php?f=21&t=2389&start=10#p25242
If your surface film is not triggered by newly introduced bog-wood then that's your problem.

After my plants got in tip top shape the surface scum disappeared completely.

Cheers,
Mike


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## mlgt

Does your tank have a lid or is it open to elements?


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## John Starkey

Ok after reading Clive,s thread on this subject i am going to up my lighting to 7 hrs as the plants are doing ok,up the TPN + as i am only dosing half the recommended dose at the moment,up the co2 back to 4 BPS,and turn up the flow rate on my filter,i will keep you posted on the results,

regards,
john.


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## John Starkey

mlgt said:
			
		

> Does your tank have a lid or is it open to elements?



Its open topped, i have never in thirty years of fish keeping had a lid on my aquariums,

regards,
john.


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## roadmaster

john starkey said:
			
		

> mlgt said:
> 
> 
> 
> 
> Does your tank have a lid or is it open to elements?
> 
> 
> 
> 
> Its open topped, i have never in thirty years of fish keeping had a lid on my aquariums,
> 
> regards,
> john.
Click to expand...



I must keep a lid over the tank or my fishes would immediately jump out  
I wish it were not so.


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## mlgt

Have you managed to resolve this issue?


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## John Starkey

mlgt said:
			
		

> Have you managed to resolve this issue?



Hi Migt,its 100% better since i upped the co2 to 4 BPS,i also upped the lighting from 6 hrs to 7 hrs,i also increased the flow rate and up to now the film is a lot better,i also upped the TPN+ to 4mls, i am struggling with the marsilea for some reason,initially it took off very well,then it seemed to be suffering from the diatom issue i was having,now the the filter has fully matured and the diatoms have gone i trimmed it right down to see if that gets it going,if not out it comes   ,

regards,
john.


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## George Farmer

john starkey said:
			
		

> the film i am getting is like a clear white film and when you pull your finger through it  it clots just like cold white fat does on water,but bare in mind it is a very thin film,
> 
> regards,
> john.


I'm getting exactly the same thing in two of my three tanks.  It comes and goes, seemingly at random times, but affects the two victim tanks at similar levels of 'scum intensity'.

Coincidence perhaps, but the only tank not getting it has a closed lid.  The two victims are open top.

I don't think this type of scum is nutrient or CO2 related, but something in the surrounding air.

The scum is pure white and has a waxy feel to it.

Does anyone else suffer from a similar type of scum?


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## Mark Evans

like I've said, it comes and goes also. Thin film, which if left unchecked, can get bad. 

Skim it off with a plastic tub (takes 2 mins) it runs clear. Over time, it then disappears all together.


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## George Farmer

What do you think is causing it, Mark?


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## John Starkey

George Farmer said:
			
		

> What do you think is causing it, Mark?




The scum is pure white and has a waxy feel to it

Thats exactly like the film was on my surface,i did notice it got better when i stopped dosing easy carbo for a week,but as an experiment i started to dose 1 ml a day and hey presto it was back in 2 days just as bad,now i am not saying that its mainly caused by easy carbo, but i think it may be an excess of co2  :?: ,since i have stopped the easy carbo its no where near as bad so really i am non the wiser as i have upped my co2,


regards john


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## Mark Evans

George Farmer said:
			
		

> What do you think is causing it, Mark?



in all honesty, i'm not sure.

My observation's tell me, when more co2 is added it can get worse (sorry Clive) but it does. 

I believe, (without scientific back up) it's instability with biological contents of the tank, or lack of it. I get it on start up, to about 7 or 8 weeks in backing my belief up. Then, as things 'settle' or stabilize, it goes... a bit like diatoms.


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## Mark Evans

here you go.

The old prairie lands a year ago. The reason i ripped it down.

chronic algae...






I got fed up with this. so left it to see what happened...





surface scum builds. leaving it deprives the tank of oxygen i reckon.









Now fast forward a year, with better knowledge, maintenance and things are different. I still get it slightly, but skim it off everyday, it'll go in time. 

Notice the lighting height to.


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## John Starkey

Mark that third shot is exactly like the film i get   ,

regards,
john.


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## Ian Holdich

i also get the '3rd' shot scum in my nano as well. I'm not injecting C02, just dosing easycarbo, i also dose profito a couple of times a week. The light is low. I also had this in an old tank, now the only thing i can see/put a link to is that i used/use zeolite in both tanks.The nano is heavliy planted with riccia and its really healthy. It doesn't bother me as i can just jug it off every couple of days.


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## ceg4048

Hi Mark,
I think you might be mixing up cause and effect. As mentioned before there is a relationship between the metabolic rate and the production of organic waste. If you feed the plants more CO2 then they will eject more waste products. So it's not surprising that more fats, oils and carbohydrates are ejected with increase metabolism due to increased consumption of CO2. The next step though is that with an increase in CO2 consumption there is a demand for more nutrients. The nutrient loading must match the CO2 loading. If the higher CO2 consumption is not matched by higher nutrient consumption, then the waste ejection is higher than normal.

CO2 metabolism is a much more complicated issue than nutrient consumption because of the Rubisco transport mechanism. You can lower the CO2, keep the same lighting and then you can observe an increase in the scum. If the CO2 was lowered only a small amount the scum may last only a few weeks as the plant adapts to the lowered CO2 level. If the new CO2 level is within the tolerance range for that lighting level then the plant can adapt. If the Lower CO2 level is too drastic for the lighting level then the plants continue to leach waste products into the water column. This then becomes a chronic issue and can lead to other CO2 deficiency symptoms.

If lighting level and nutrient levels are held constant, but if CO2 is increased, then this could lead to a demand for higher nutrient uptake. If this is not met then the excess ejection is caused by nutrient deficiency. Again, depending on how much more CO2 is being consumed, this determines the severity of the nutrient deficiency. If the increase in CO2 is mild to middling, then after a few weeks the plant has the ability to adapt by becoming more efficient at nutrient uptake. If the CO2 increase is significant then this may fall outside the range of the adaptability.

So it's very difficult to predict exactly how many ppm of this or that will result in excessive or normal ejection because of the range of adaptability and the degree of movement in all the associated variables. Not only are the environmental variables changing, but the plant themselves are changing. They increase in mass by growing, or decrease in mass by trimming or by loss of weight due to deficiency. So the same conditions may be present in two tanks but the symptoms may only appear in one tank due to lower bio-mass in one tank versus the other. Their energy reserves may be high or low which affects the speed and duration at which the symptoms appear or disappear. In order to get to the root of the problem one has to be able to control all variables in the equation, and that simply doesn't happen. People become impatient because we all want a quick fix. And that's why we draw these premature conclusions.

I use tons of CO2 and I don't have any of these issues. I can add more CO2 and the only thing that happens is more health, clearer water and more pearling. In my case I don't have to make any adjustments to nutrient levels because they are already unlimited.

This problem also has been reported in non-CO2 tanks. So the conclusion that this is caused strictly by CO2 can't be true unilaterally. This is an illusion and we simply haven't figured out the magicians trick.

In this shot I turned the filters off for a few hours to see how much oily film was actually present. There was very little, although you could see a thin film.


 
So generally, it really depends on where you are in terms of plant health and nutrition, not just "did I add more CO2", even though it might appear so at face value. Health and nutrition are always going to be linked to lighting intensity, flow/distribution, nutrient levels, bio-mass and so forth.


Surface film does not always deprive the tank of Oxygen. The film block gas transport across the air/water interface. Therefore, if the plants are producing Oxygen during the photoperiod, then less oxygen escapes to atmosphere. If the Oxygen level falls below atmospheric levels during the night then yes, the film does lower Oxygen ingress into the tank. The same goes for CO2.

It wouldn't be surprising at all that algal blooms in the tank are either accompanied by, or preceded by surface scum, because these are both health and nutrition related. In fact, typically one gets the film and then the algae. The film is a harbinger of doom because it's telling you that you have health issues.

Cheers,


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## Garuf

I had the same film and I attributed it to crypts, as soon as I removed the crypts the film went, never noticed it with any other plant but crypts before or since though I see that I must have lowered the co2/nutrient demand by removing them and not seen the true reason for the film. I think it might be a natural part of start up to an extent, plants will be melting/shedding old leaves etc but I could be wrong?


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## dw1305

Hi all,
I think the surface scum is mainly "biofilm" as well. My thoughts are that the plants are naturally quite "leaky" and produce lipids, carbohydrates etc. The scum is formed when these compounds build up, and are colonised by bacteria etc. It actually has a scientific name, the "neuston".

This is from Brett the Skeptical Aquarist, who is a much better writer than I am. 





> In fairly still ("lentic") waters, surface tension creates a stable environment for organisms and offers the best access to carbon dioxide and oxygen in the air. The density of living cells on the surface may be ten to a hundred times what it is in the water layers just beneath the surface slick. Many bacterial strains in this biologically-enriched surface layer carry photosynthetic pigments, though you might not notice cyanobacteria, for example, until they stain your paper towel blue-green. There are also true algae, diatoms, fungi and single-celled protozoans in these organically-enriched microlayers.


A surface skimmer or daily paper towel wipe or increased flow or increased water changes will remove it, and if you combine low-tech and water changes you don't get it at all.

Another possibility is that the aquarium is open topped? in which case the film may also have oil or wax droplets from cooking, furniture cleaner etc or even bio-particulates from the terpenes and propellants in aerosols.

cheers Darrel


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## mlgt

Funny that you mention crypts as I do have crypts in my tanks. However this has only stared happening when the weather has gotten colder.

I notice that my tubs of moss by the window sill also have a film on top of the water. Weird. I now do daily water changes with my main tank water to ward this off. 

Sadly my nano is open toppped and low tech. Lighting is around 6 hrs a day and I have a hob filter.


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## NeilW

This has been the bane of my tanks life too at the moment.  Both Garuf's and migt's findings with crypts are true to me also.  I believe my problem is still a lack of flow delivering CO2 so I'm going to try ditch the crypts as a solution and make it a completely moss tank to reduce CO2/nutrient demand.  Interesting post.

Cheers,
Neil


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## tyrophagus

I don't have a chemistry degree but I have to wonder what adding EI ferts + high levels of co2 to a tank do to the water chemistry. 

I was once told that the scum on top of the bath water was mostly calcium carbonate.  

How do all these salts and co2 interact in the water column before we consider the substances released by the plants if they're in suboptimal health?

My water has loads of calcium in it.  If I add lots of co2 will they interact?


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## nry

I've had surface film/scum with EI/High Tec and non-EI/Low Tec, so I can't link the two together.


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## GHNelson

Hi
Noticed that if there is very little surface movement this surface scum rears it ugly head.
That's in both cases high tec and low tec.
If you use a air stone at night when the Co2 has switched off I bet you don't get this film on the surface in the morning.
hoggie


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## ceg4048

NeilW said:
			
		

> This has been the bane of my tanks life too at the moment. Both Garuf's and migt's findings with crypts are true to me also.


Well, I mean if you have a big plant and it's suffering then this plant will contribute to the problem, but don't blame it on the plant. Fix the real problem. I've had loads of crypts and don't have this problem, so it can't be due to crypts. 





			
				NeilW said:
			
		

> I believe my problem is still a lack of flow delivering CO2 so I'm going to try ditch the crypts as a solution and make it a completely moss tank to reduce CO2/nutrient demand.


OK, so have you considered the benefits to the tank of healthy crypts and what it is that you're giving up by ditching them? How about lowering the light intensity? How about experimenting with the nutrient levels?


			
				tyrophagus said:
			
		

> I don't have a chemistry degree but I have to wonder what adding EI ferts + high levels of co2 to a tank do to the water chemistry.


It does lots of things but it only indirectly affects surface scum.


			
				tyrophagus said:
			
		

> I was once told that the scum on top of the bath water was mostly calcium carbonate.


Calcium Carbonate is the substance in your tap water that causes the water to be both high in Carbonate hardness (KH) as well as General Hardness (GH) from the Calcium. Calcium Carbonate is easily dissolved by acids, and in nature, dissolved CO2 in groundwater generates Carbonic acid which then dissolves the CaCO3 and that's how it gets into your tap water supply. Calcium Carbonate is otherwise known as Limestone, or Chalk. There are no relevant interactions of the nutrient salts with CaCO3, however one trick when taking a bath is to add Epsom Salts (MgSO4) to the bath water which helps to prevent soap scum. High CO2 concentration in the aquarium water means high Carbonic acid content which dissolves the CaCO3 and keeps it in solution. You're barking up the wrong tree if you think EI is responsible for surface scum, which is made of oils and other carbon products.

You see these EI fed crypts? The tallest lances are 2 feet long. They are shown in the peak of health as you can see by the sheen of the leaf surface. There is no algae and the water's surface is immaculate. Linking EI to surface scum is like blaming algae on nutrients.

Have you ever seen that TV series Kung Fu? The one with David Carradine? Remember when he first entered the Temple and had to snatch the pebble from the master's hand? Well guess what? This is your pebble. When you can grow crypts that look like this then you automatically won't have surface scum. If you've got surface scum you must have the discipline to blame your own poor technique. Just because you added CO2 it doesn't mean that you added enough. Just because you added more flow it doesn't mean that you added enough. Just because you added nutrients it doesn't mean that you added enough.
Always start with lighting as suspect number 1.





Cheers,


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## mlgt

Nice analogy


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## PM

Yeah I get this on both my tanks - high tech EI & super-low tech nano.

I gave up trying to fix it long ago. I have a surface skimmer on the hi-tech, and paper towel the nano. It's not as bad as it has been before, but still appears if left.


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## nry

I find a quick scoot over with a small aquarium net clears it quick enough and is less messy than paper towels.

I actually notice that from the water change day when the scum is gone, then it builds up over the week, that by the end of the week the fish can begin to hang around the top of the water more often so I can only assume it is affecting either oxygen getting in to the water and/or CO2 getting out.


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## mlgt

Does the "fats" produced when you move your finger the film do any harm to the fishes?

Reason I asked is I would blow at the floating plants if they were to get caught up in the corners and when doing so a lovely while substance from the film falls into the tank.


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## ceg4048

Well these products rot, attract bacteria and may ultimately result in ammonia production depending on content, so while they may not directly be a hazard they are organic waste which is not good generally.

Plant cells are typically constructed of a membrane called a "bi-lipid layer" also called "phospholipid" layer. This is a compound consisting of two fatty acid chains linked to a glycerol molecule (glycerol is similar to glycerin, that sweet viscous clear liquid.)




In this photo you can see where the "bi" name comes from. The white "head" is the glycerol and it's attached to two orange "tails".  These tails are the lipids. The membrane consists of two sheets of these molecules inverted so that the fatty acid or lipid tails touch, but the heads are on the far side. In this photo the lower white heads face the inside of the cell and the upper white heads face the outside of the cell.

The white glycerol+phosphate heads are polar. That means they have an varying electric charge across the shape of the head. Phosphate is highly polar and helps this function of the head. Water is also a polar molecule. In fact it's one of, if not THE most highly polarized liquid on the planet. Waters polarity is one of the things that makes it the most amazing liquid. This means that the negatively charged part of a water molecule is attracted to the positively charged side of the white head. This polar attraction is what makes things soluble in water. Things that are soluble in water are called "hydrophilic" i.e. water-loving.

The fatty acid orange tails are non-polar. Fats, lipids and oil are all non-polar. They have no attraction to water. That's why oil and water do not mix. That's why oil, being lighter than water floats. Non-polar substances that are not attracted to water are called "hydrophobic" i.e afraid of water.

The plant cell membranes are therefore both hydrophilic and hydrophobic at the same time. This property allows the cells to be selective about which chemicals can enter or leave the cell. For example, the white heads mix with water, and so objects that are dissolved in water can be carried to, and attracted to the heads but the water cannot penetrate the central lipid layer because it's basically made of oil, which rejects the water and therefore rejects any other polar substance dissolved in the water.

In order to select specific chemicals the phospholipid layer is studded with "channels" which are just various proteins which are designed to have special attraction to specific chemicals. When those chemicals are dissolved in the water and touch their favorite channel they are pulled into the channel and avoid the lipid tails by traveling through the protein as if they were traveling through a tunnel. Here is a schematic of channels studded across and through a bi-lipid layer:


 

The fatty acid tails and the  proteins studding the cell membrane are the source of polyunsaturated fats. This is exactly why eating vegetables and leafy plants are good for you. This is the source of vegetable oil. Plants that die and become fossilized under great pressures underground have their lipids converted to a hydrocarbon form we call crude oil. Plants are the source of your petrol. This is why petroleum is called fossil fuel.

When the plant is under nutrient and/or CO2 stress their cells rupture. What you then see on the surface are the lipid tails and fatty acid products destroyed and spewed out. The hydrophobic nature of the tails send them to the surface. This is a combination of pre-petroleum and glycerine products floating on the surface, telling you that the plants are under duress.

Paper towels, fish nets and skimmers do not solve the basic problem of environmental stress. The proper path is to solve the malnutrition or to reduce the lighting to lower the nutrient/CO2 uptake demand.

Cheers,


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## Anonymous

Thank you ceg for the in depth presentation 



> Paper towels, fish nets and skimmers do not solve the basic problem of environmental stress.



True, although the surface extractor is good to get rid of dust and food from the water surface before photo sessions  



> The proper path is to solve the malnutrition or to reduce the lighting to lower the nutrient/CO2 uptake demand.



True, this is the best approach and works every time.

Cheers,
Mike


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## mlgt

Wow. A lesson in science first thing in the morning is great. I had to read it twice but its great knowledge to be had.
Thanks for the in depth reply and knowledge share


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## John Lumb

George Farmer said:


> I'm getting exactly the same thing in two of my three tanks.  It comes and goes, seemingly at random times, but affects the two victim tanks at similar levels of 'scum intensity'.
> 
> Coincidence perhaps, but the only tank not getting it has a closed lid.  The two victims are open top.
> 
> I don't think this type of scum is nutrient or CO2 related, but something in the surrounding air.
> 
> The scum is pure white and has a waxy feel to it.
> 
> Does anyone else suffer from a similar type of scum?


Hi George,

Yes, funnily enough, I do. 

I actually noticed this yesterday and my Aqua Nano30 fishless aquarium has a similar scummy/film on top. I agree it is milky in colour and appears mainly if I leave the lid off.
I did think it was related to my CO2 dosing and possibly the issue with Glutarahalderide as you have mentioned before. 

I have changed it from having a few fish to at the moment a fishless tank with just some Bogwood Java Fern, Moss and Vallis which I took from my other tank as 'grown on' plants it is under a 7W led light with a small nano filter on its lowest setting and occasional airstone action. I would love to find a perfect very fine mist bar about 7-10" long to work slowly in the rear but cannot find one for love nor money, and with a lack of aquatic shops near me now I am struggling.

The tank is in the kitchen near a window which is West facing and dulled severely by neighbours very high bushes so little natural light. The oven/Hob is about 10-12' away from the tank and obscured by an American style fridge so I assume very little in the way of air particles being put into the water.

Parameters:

Water = Wet
PH        = 7
NO3    = Very Low = 10? (very much depends on the stick current API is in between 0 & 20)
NO2   = 0
GH      = > 180 Very Hard (Typical South West London water, I live nr Twickenham)
KH      =  0

There are some algae on the Vallis and old peat dust from the substrate which has broken down over 2 yrs or so. 
Water does have a slightly dusty look too it is not crystal clear like your tanks which I am very very sad about and have no idea what to do.

Would I be better to actually strip the tank down and re-scape it before I add a Betta which is what my darling better half wants even though I want Ember Tetras and some Pigmy Corys?


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## jaypeecee

Hi @John Lumb 

There are some clues earlier in this thread as to potential causes of surface film and you could also take a look at:






						Do Healthy Plants Release Organics?
					

Hi Folks,  I am trying to get a full(er) picture of what contributes to dissolved organic carbon (DOC) in freshwater aquariums. Why? Well, I still have an ongoing problem with an oily film on the water surface. Using the kitchen paper towel method is effective but the result is short-lived. I...



					www.ukaps.org
				




But, in your case, I wonder if the kitchen environment is contributing to/causing the surface film. To some extent, it may depend on what air extraction you have in the kitchen. If there are invisible airborne droplets of organic compounds in the air (from cooking), perhaps these are collecting on the tank water surface? I see that it is an open-top tank. My hunch is that a surface skimmer may be the way to go. These pieces of kit are discussed frequently on UKAPS. If you don't have shrimp and small fish, the Eheim _skim350_ is one possibility. Another, possibly better (and cheaper) option is the All Pond Solutions _Skim-2_.

JPC


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## John Lumb

jaypeecee said:


> Hi @John Lumb
> 
> There are some clues earlier in this thread as to potential causes of surface film and you could also take a look at:
> 
> 
> 
> 
> 
> 
> Do Healthy Plants Release Organics?
> 
> 
> Hi Folks,  I am trying to get a full(er) picture of what contributes to dissolved organic carbon (DOC) in freshwater aquariums. Why? Well, I still have an ongoing problem with an oily film on the water surface. Using the kitchen paper towel method is effective but the result is short-lived. I...
> 
> 
> 
> www.ukaps.org
> 
> 
> 
> 
> 
> But, in your case, I wonder if the kitchen environment is contributing to/causing the surface film. To some extent, it may depend on what air extraction you have in the kitchen. If there are invisible airborne droplets of organic compounds in the air (from cooking), perhaps these are collecting on the tank water surface? I see that it is an open-top tank. My hunch is that a surface skimmer may be the way to go. These pieces of kit are discussed frequently on UKAPS. If you don't have shrimp and small fish, the Eheim _skim350_ is one possibility. Another, possibly better (and cheaper) option is the All Pond Solutions _Skim-2_.
> 
> JPC


We have a full extraction system out of the kitchen and normally I actually keep the glass lid on the tank. I was replying to the earlier thread though I was wondering if the recent disturbed Aquatic soil had caused this issue as it had not occurred before


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## jaypeecee

John Lumb said:


> We have a full extraction system out of the kitchen and normally I actually keep the glass lid on the tank. I was replying to the earlier thread though I was wondering if the recent disturbed Aquatic soil had caused this issue as it had not occurred before


Hi @John Lumb 

OK, so maybe it's nothing to do with the kitchen. One of the reasons I thought it might be kitchen/environment-related was because of what you said below:


John Lumb said:


> I actually noticed this yesterday and my Aqua Nano30 fishless aquarium has a similar scummy/film on top. I agree it is milky in colour and appears mainly if I leave the lid off.


If the milky colour appears when the lid is off, that seems significant, doesn't it?

JPC


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## not called Bob

its almost always fatty acids from decaying matter


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## rebel

My unbiased view is that we should call it Rebel Scum.


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## John Lumb

Well to avoid the 'Rebel Scum' I have decided to replace the glass lid and I am aerating the aquarium though it does not need it, I just like to see some nice gentle bubbles while I work.


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## dsandson

John,

I have just set up my Aqua Nano 40 (next step up from your tank) and found that i was getting some of this surface scum. May not be the same source but I have found the back filter can help if you get the grille intake to act more as a weir.

I have dropped the water level slightly. This has a result of letting less water through to the filter compartment, and the pump then lowers the water. If you keep the water lower in the filter side it will act as a weir and take the surface scum into the filter. Its not a very stable situation and minor evaporation will lower the filter level further and cause the pump to blow air,  so keep it topping it off if you want this set up over a longer period.


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## Wolf6

I have the eheim skimmer with the eheim shrimp guard, comes on 30 minutes in the morning before lights on, 30 mins in the evening after lights out, havent seen any scum since on this tank ever since I got it. My larger tank has a skimmer on the filter inlet, but that one is a bit dodgy, I have to constantly monitor it, too high or too low and it doesnt work well. 
I do have to say I've only encountered scum in tanks I run with CO2. I've had periods where I neglected the tank, CO2 ran out and I didnt replace, and the scum disappeared. But I believe Ceg's explanation as to why this is


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