Surface Scum

[aamir9110]

Hi all, I have a question about my planted tank, but first let me introduce my background. i started a "fish" tank 5 years ago since my lovely wife demanded a gold fish of her own. For the next 2 1/2 years i grew a lot of algae and the goldfishes did grow fatter, the moved from their 5 Gal ( woefully inadequate) tank to their new home - a 20Gal long, meanwhile I did put a few plants here and there picked up from the LFH (petco) and they grew lovely hues of various kinds of algae. Then a while ago i came across - Planted aquariums - and i was quite smitten, dreamt many nights to have my goldfishes live in the midst of a natural setting. Then came Barrreport and thus I got my first experience at growing plants!!

Heres my first attempt:
photo.jpg

20Gal tall
Eheim 2213
Airgas dual regulator - sumo post kit with Ideal valve
Koralia for surface movement
Hydor 200W inline heater 78 deg
Danner NW 3 inline with CO2
Light - Catalina 48Watt ( only has 1 tube on for 10 hrs and 2nd on for 5 hours midday)

EI 2 - 4 times weekly
WC 2 - 4 times a month ( sadly a BUSY life )

12 neon tetras
4 SAE - will find a bigger home soon.

I am fairly happy with the setup ( wifee recently gave permission for a new 100Gal tank as well )

The problem is an oily skin at the surface. Drop check is nice and limy green , flow is great ~ 500 gal/hr total for a 20gal tank, and there is the tiniest amount of visible algae anywhere on new leaves (many plants came from a algae loaded fish tank)


The problem is that for the last few days I am noticing a thin oily covering the surface that needs to be manually skimmed and keeps coming back.
I at the moment have no time of means of checking CO2 or nutrient levels ( 14 hour work days! )
I dont know what else to provide as info!
Thanks beforehand for your replies and insight.

plantweed.

[Mark Lem]

I've had that also, thats why I'm going to sump and surface skimmer intake on my new tank. I find it gets worse when I am near needing a water change and also seems to get worse when i feed live worms...

[ShadowMac]

I've found nightly aeration works to keep it away. Before I go to bed I lift up my lily pipe so it agitates and aerates the surface. This keeps it away. Its quite common. My 7 gallon cube runs an HOB filter only at night to break up the film, a small canister is the primary filtration. No surface film here either.

[wilsar]

dont know if im gonna get shot down for this but this scum film is the beginning of cyanobacteria, which would indicate that K is overstepping its balance with N.

[ShadowMac]

wilsar, I see gunsights in your future...


the surface film is a bio-protein layer and as far as I know has nothing to do with cyanobacteria. Also, Tom has stated quite a number of times in various places that ratios are not important. He has said ratios are used in industrial fertilizer and farming since such large quantities apply. Leibig's Law of the Minimum applies to our tanks in regards to nutrients. Tom knows WAY more than I so I am paraphrasing his statements. To me and my bit of knowledge the Law of the Minimum makes intuitive sense and is quite commonly applied in many biological systems.

[wilsar]

has anybody tested my theory of allowing the bio film to remain and increase and what the final result would be? i didnt say the film was cyanobacteria itself but would lead towards its manifestation. the excess of protein molecules within the low oxygen environment needs to be broken down and it is with the denitrification process that heterotrophic bacteria/fungus will be useful. my words on K being out of balance with N was maybe confusing as this is a conclusion taken from of the end result.

there are other bacteria which feed of this bio film which are hazardous to health. here is a pdf http://tinyurl.com/cuj6b2q Mycobacteriosis- the Stealth Disease

[ShadowMac]

There is no reason to test because the statement can be easily falsified. I have run many tanks with the film, which is so common in planted tanks that ADA makes a surface skimmer, without any cyanobacteria. Correlation does not infer causation, just because something can be found alongside another thing does not mean they cannot be mutually exclusive.

There is another issue with allowing the film to remain and generally allowing the tank parameters to go to crap as a method of experimentation. There are so many confounds you could not clearly conclude the film was the cause or even the start of the problem. A thick surface film may be signs of other things ie high DOC, low gas exchange, poor flow, etc. A lot of these things can lead to cyanobacteria...other things as well like high light which have nothing to do with surface film. How many of these do you need to get cyano? How many do you not need? which combination? which is most important? all of these things could not be concluded. I can say with reasonable certainty that surface film is not a contributing factor in cyano growth.

I see where you are going with this, however the reasoning is flawed. Cyanobacteria can occur in tanks without surface film.

I'm not sure what you mean by balance of K and N if not a ratio. Could you describe what you meant?

EDIT: I see you added a link to Diana Walstad's article. Thanks, it was a good read.

[Tug]

It's the, if I wash my hair tonight, the sun will come up in the morning hypothesis.

[wilsar]

the sun will rise whether i wash my hair or not.

Cyanobacteria can occur in tanks without surface film.

I'm not sure what you mean by balance of K and N if not a ratio. Could you describe what you meant?

true that cyanobacteria occurs in tanks or environments that have no surface film present and a bio film does not necessarily produce it but where it does manifest is within the bio film itself, whether upon the rocks, plants or water surface. the biofilm community will in itself be the director of such occurrence.

after a cyanobacterial infestation, the nitrogen is released into the atmosphere and creates a depleted zone of such element. one could question why and conclude that the system had an incorrect balance of nutrients and needed to be readdressed by natural occurrence within the system as a whole. referencing the redfield ratio with algae control, this balancing can be addressed between the two elements K and N.
the imbalance is within the biofilm and the denitrification process of atmospheric nitrogen being released.
as i stated i will probably be shot down and i now need a parachute.

[ShadowMac]

I think what you are describing would lend itself more to the Law of the Minimum, as again the redfield ratio is a ratio and ratios do not apply to our systems. By imbalance we could substitute the word shortage, or deficiency, and arrive at the law of the minimum. The system is only impacted by the lack of something not by there being more of something compared to another something...too much K to N. If you do not have enough N, you will end up with growth problems and algae. I'm not totally certain that the cyanobacteria we find in our aquariums is one in the same or similar enough to the atmospheric nitrogen fixing cyanobacteria of the terrestrial realm. Tom would be able to shed light on that, but I do believe I have heard that mentioned. the BGA we find in our tanks is photosynthetic therefore fixes carbon for energy using photosynthesis. I think it has another metabolic route but in most tanks will not need to take that when light is available.

We can conclude, and agree, that biofilm is usually if not always present in a tank. Shrimp are known to relish the stuff. However, cyanobacteria is not always present, leading us back to where we started.