Surface scum/protein and CO2 outgassing - The Planted Tank Forum
 
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post #1 of 13 (permalink) Old 01-13-2011, 10:33 PM Thread Starter
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Surface scum/protein and CO2 outgassing

Has anyone noticed a lot of surface scum and reduced CO2 outgassing? I only ask because in the past month I have had bad surface scum. Yesterday I got three black mollies and this morning the scum is all gone (good job mollies). However, I noticed my bubble count cannot seem to keep a constant CO2 concentration (using a controlller) and I've had to pump up the bubble count a lot today and it's still not where it should be.
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post #2 of 13 (permalink) Old 01-13-2011, 10:39 PM
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Pointing a powerhead or pump at the surface will help with the surface scum. It will bring it down intot he water column where the filter can deal with it.

But at the same time you will lose more CO2 that way. So it's kind of a trade off.

One solution would be to point a pump at the surface and have it on a time to only come on at night. Or in the mornign before the CO2 comes on. That will keep the scum down and then you can have a calm water surface to keep your CO2 in durring the day.
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post #3 of 13 (permalink) Old 01-13-2011, 10:59 PM Thread Starter
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Quote:
Originally Posted by mmelnick View Post
Pointing a powerhead or pump at the surface will help with the surface scum. It will bring it down intot he water column where the filter can deal with it.

But at the same time you will lose more CO2 that way. So it's kind of a trade off.

One solution would be to point a pump at the surface and have it on a time to only come on at night. Or in the mornign before the CO2 comes on. That will keep the scum down and then you can have a calm water surface to keep your CO2 in durring the day.
I have a 700gph pump moving water and good surface ripple in a 75 gallon - still had scum. I don't have the scum anymore - mollies do a good job scurying around the surface chopping up the scum.

I was bringing up the question if scum will decrease CO2 outgassing.
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post #4 of 13 (permalink) Old 01-13-2011, 11:01 PM
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Originally Posted by helgymatt View Post
I was bringing up the question if scum will decrease CO2 outgassing.
Sorry I missed that part.

Good question.
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post #5 of 13 (permalink) Old 01-13-2011, 11:47 PM
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Yes, it definitely reduced CO2 outgassing, it also, more importantly, reduces all gas exchange, so O2 is less also.

I've noticed this a fair amount on my 180 gal tank.
If I leave the lids on the tank, I can get a similar case even without any scum.

When the O2 production from plants is high, there's less scum as well.

You can see how much reduction the water surface moves without scum layers.
The reduction in flow of surface turnover is very high even with high flow rates.

I have zero movement or without the scum, I get about 20 cm a second on the surface. That's a huge difference. It is also measurable and measurable as far as the night time degassing.

The tank never dips below 25ppm of CO2 at night with the scum layer, without, 15ppm or so. O2, the min max ranges are higher with the scum, without, much less extreme. I also noted that with the lids on, I had much less scum layer formation.




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post #6 of 13 (permalink) Old 01-14-2011, 01:09 AM
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What i do is let my CO2 turn off a night and let my air pump turn on. It will create surface movement and prevent surface scum. It will also reset your tank.
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post #7 of 13 (permalink) Old 01-14-2011, 02:01 AM Thread Starter
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Originally Posted by plantbrain View Post
Yes, it definitely reduced CO2 outgassing, it also, more importantly, reduces all gas exchange, so O2 is less also.

I've noticed this a fair amount on my 180 gal tank.
If I leave the lids on the tank, I can get a similar case even without any scum.

When the O2 production from plants is high, there's less scum as well.

You can see how much reduction the water surface moves without scum layers.
The reduction in flow of surface turnover is very high even with high flow rates.

I have zero movement or without the scum, I get about 20 cm a second on the surface. That's a huge difference. It is also measurable and measurable as far as the night time degassing.

The tank never dips below 25ppm of CO2 at night with the scum layer, without, 15ppm or so. O2, the min max ranges are higher with the scum, without, much less extreme. I also noted that with the lids on, I had much less scum layer formation.
Even with a big ripple in the surface, I would still have scum all day (worse towards the end of the light cycle). The only area clear of scum would be the area just around where the surface was broke. Now, with the scum gone, the entire water surface moves around. It's amazing to me that a few mollies can do better at breaking up the surface scum than a pump trying to make good surface disturbance.

This should be an informative thread to many - I have never seen this issue discussed before in any threads.
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post #8 of 13 (permalink) Old 01-14-2011, 10:22 AM
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When I do water changes I scoop the water from the top instead of using a gravel vac. I know this leaves me with more detritus but I never have problems with biofilm on the top.
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post #9 of 13 (permalink) Old 01-14-2011, 01:42 PM Thread Starter
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When I do water changes I scoop the water from the top instead of using a gravel vac. I know this leaves me with more detritus but I never have problems with biofilm on the top.
My experiences are you either have it or you don't. I'll go months with no scum and then one day it's back. I'm fairly certain what brought it on this last time was toxins in the air from paint and stain fumes. I ended up with very thick scum the next morning, dead fish, and bacteria bloom. That was about a month ago and conditions with the scum have slowly improved. I would use paper towels and suction off the water from the top and the scum would be back within hours.
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post #10 of 13 (permalink) Old 01-14-2011, 10:13 PM
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Quote:
Originally Posted by helgymatt View Post
Even with a big ripple in the surface, I would still have scum all day (worse towards the end of the light cycle). The only area clear of scum would be the area just around where the surface was broke. Now, with the scum gone, the entire water surface moves around. It's amazing to me that a few mollies can do better at breaking up the surface scum than a pump trying to make good surface disturbance.

This should be an informative thread to many - I have never seen this issue discussed before in any threads.
Mollies are good, I do not doubt them




Regards,
Tom Barr
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post #11 of 13 (permalink) Old 01-15-2011, 12:19 AM
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I recently did a large rescape of my tank and the very next day I had surface scum. The only difference was the plant load, it dropped considerably. Before surface was like a mirror and afterward it has been….bad. I am hoping that when my tanks plant load grows that the surface scum issue will pass.

I just wish someone could explain what causes it. Is it low oxygen?
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post #12 of 13 (permalink) Old 01-15-2011, 12:46 AM
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Whenever I remember, I slide the end of my spraybar (already pointed upwards) up a couple inches at night after the photoperiod, and scum is gone by morning. Gotta remember to slide it back down, of course.
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post #13 of 13 (permalink) Old 01-15-2011, 03:11 PM Thread Starter
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Quote:
Originally Posted by The Plantman View Post
I recently did a large rescape of my tank and the very next day I had surface scum. The only difference was the plant load, it dropped considerably. Before surface was like a mirror and afterward it has been….bad. I am hoping that when my tanks plant load grows that the surface scum issue will pass.

I just wish someone could explain what causes it. Is it low oxygen?
The same thing happened to me after rescaping. From what I understand the scum is organics/protein. When disturbing the substrate and changing the tank around much of the organics became distrubed and thus you have a scum problem. Give it a few weeks and the scum should subside - water changes also good. Try a few mollies.
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