# When exactly does pearling happen?



## wonder woman (Apr 8, 2004)

When, exactly, does pearling happen? Is it pretty much a constant thing in flourishing planted tanks, or is there a specific time at which this happens? 
I'm asking, because for the whole day right after I do a 25% water change in my tank, I see tiny little bubbles all over my plants. At first, I had thought that this was just extra oxygen (or chlorine gas???) escaping from the new water I just added, but I do add conditioner, so I wouldn't think there'd be that much that would stick around for that long. 
Thanks in advance!


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## gpodio (Feb 4, 2004)

Pearling occurs when the water is saturated with oxygen and additional oxygen produced by the plants simply forms a bubble and floats to the surface rather than being dissolved into the water. This occurs at different times depending on the rate of growth and oxygen levels during the night, but in general it occurs more towards the end of the light period or at least in the second half.

When you do a water change a similar thing occurs due to the pressure the tap water is held in the pipes. This saturates it with gasses and will therefore appear to make the tank pearl temporarily. If this continues longer than say half a day, I'd say that the plants are also contributing to the extra pearling and the tap water you added may be providing some trace elemenets that the plants were in short supply of prior to the change. This is evident when you do a water change and plants pearl like mad for a couple days then taper off until the next water change.

Hope that helps
Giancarlo Podio


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## Maurici (May 31, 2004)

But the different species of plants have their own speed to make bubbles, do you think it depends of the thickness of the cuticle or epidermis cells walls or depends of the entire leaf thickness or depends of their particular use of the O2 produced by their photosynthesis?. Thanks. Maurici.


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## ShaneSmith (Feb 15, 2004)

I think where the bubbles comes from might have something to do with the leaf thickness. But as far as i know the photosynthesis rate of the plant is what controls bubbling ability.


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## wonder woman (Apr 8, 2004)

Bummer- it sounds like I've just got gas :wink: Guess I'll have to wait until I go pressurized to see REAL pearling. Thanks for the help!


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## gpodio (Feb 4, 2004)

Maurici said:


> But the different species of plants have their own speed to make bubbles, do you think it depends of the thickness of the cuticle or epidermis cells walls or depends of the entire leaf thickness or depends of their particular use of the O2 produced by their photosynthesis?. Thanks. Maurici.


All plants release oxygen during photosynthesis, you just don't see the bubbles until the water is saturated. While I'm sure each plant has it's own rate and various properties of the plant may govern the rate of oxygen release, I think the growth rate is probably the biggest influence. Fast growing plants like many stems, riccia and glosso pearl a lot more than slow growing plants such as anubias and crypts for example. The more fast growing plants you have, the sooner your tank will reach oxygen saturation and begin to pearl.

Giancarlo Podio


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## Maurici (May 31, 2004)

Hello, gpodio, I agree with your comments about the need of water saturation on O2 to pearl, but I would focus the pearling effect on the specie and the O2 saturation on the boundary layer rounding each leaf. I think there is no a fact related with the entire column of water saturation because this will imply the bubbling of every plant of the tank (which is no the reality) taking on account that all of them are making photosyntesis. It's seems quite right taht it must depend of the speed of growing, it is interesting, thanks. Maurici.


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## ShaneSmith (Feb 15, 2004)

my wendtii has traditionally been one of my heaviest pearlers in tanks with Hygro difformis Hemianthus umbrosum Limnophila Aromatica Rotala green etc... Wendtii has had a tendency when in full light to pearl as much if not more then these.


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## Jeff Kropp (Apr 25, 2004)

ShaneSmith said:


> wendtii has traditionally been one of my heaviest pearlers


Lets make a distinction between pearling and streaming.

Crypts are big streamers from damaged spots on leaves or roots. They will stream a bubble size proportionate to the hole of origin. Streaming is not dependant on O2 saturation and will begin a few minutes after lights on. Often streaming will catch under the leaves of taller plants and look like pearling from those plants.

Riccia is a notorious pearler. It will begin forming small bubbles several hours after lights on. These bubbles begin small and grow till large enough to break away, they do not form streams of bubbles. Pearling is dependant on localized O2 saturation.

Shane are your crypts streaming or pearling?

___
Jeff


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## ShaneSmith (Feb 15, 2004)

Streaming. I guess i was wrong. Then Rotala Macranda green is my heaviest pearler. I want to know is streaming unhealthy?


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## MiamiAG (Jan 13, 2004)

No, streaming is a natural event and is not harmful.

Here's a quote:


> In terrestrial plants stomata play an important regulatory role during the gas exchange of water, oxygen and carbon dioxide. Not so in aquatic plants where the permeation of gases through membranes constitutes the decisive process. Here the diffusion rate of a gas is proportional to the difference of the concentrations of the gas concerned inside or outside the membrane. If the CO2 concentration in water is 20mg/l at one stage and 2mg/l at another - under conditions of powerful light exposure - then the diffusion rate as well as the rate of photosynthesis will be ten times lower in the second case, assuming that the CO2 concentration within the cell will be very low under light exposure due to photosynthesis. During oxygen transportation from the cell the ratios should be similar. If, for instance, the oxygen concentrations within both the cell as well as the water measure 8mg/l each, diffusion will not occur. A drop or gradient in the concentration level has to be in place before oxygen permeates. If assimilation bubbles are visible, the oxygen concentration within the cell has to measure way above 40mg/l - which is equivalent to the balanced concentration of pure oxygen in water at a temperature of 25°C - because the gas bubbles contain mainly oxygen and not air.


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