What causes pearling?

VaughnH

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Oxygen is only slightly soluble in water, so if a plant produces oxygen faster than it can be dissolved into water, a "pearl" of oxygen results.
 

aquabillpers

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VaughnH;30804 said:
Oxygen is only slightly soluble in water, so if a plant produces oxygen faster than it can be dissolved into water, a "pearl" of oxygen results.

Is their a relationship between the amount of O2 already in the water and "pearling"?

It used to be said that pearling would only occur when the water contained all of the O2 that it could hold, but I think that is no longer considered accurate.

Bill
 

stevie D

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I was wondering the same thing. I only get slight pearling after a large waterchange. I do know my DO level is not that high due to high fishloads so i am wondering if this is the case. Soon i will be moving most of the fish out of this tank to another and will see if this has any impact on pearling.

Stevie D
 

VaughnH

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Not all pearling is those big beautiful bubbles either. Some plants "pearl" with tiny little bubbles that are barely visible, while plants with big leaves tend to collect oxygen under them in bubbles that finally get big enough to be very obvious.
 

helgymatt

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When does it occur?
In my experience pearling will be highest when CO2 is optimum. I have high light and good ferts so those also play an important role.

When my CO2 is good I have amazing pearling, when CO2 is not optimum, like when a tank runs out or when the concentation is just not high enought, I get little to no pearling.

Remember that just because a drop checker is green, that doesn't mean that you have enought CO2. It is just an indicator. My drop checker is usually yellow-green when CO2 is highest at days end.

Try to bump up your CO2 slightly and see what happens. Keep a very close eye on the fish! My pH in my tank goes from 7.2 to about 6.3 after the CO2 has been on for a while.

Hope this helps,
Matt
 

aquabillpers

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helgymatt;30836 said:
When does it occur?
In my experience pearling will be highest when CO2 is optimum. I have high light and good ferts so those also play an important role.

When my CO2 is good I have amazing pearling, when CO2 is not optimum, like when a tank runs out or when the concentation is just not high enought, I get little to no pearling.

Remember that just because a drop checker is green, that doesn't mean that you have enought CO2. It is just an indicator. My drop checker is usually yellow-green when CO2 is highest at days end.

Try to bump up your CO2 slightly and see what happens. Keep a very close eye on the fish! My pH in my tank goes from 7.2 to about 6.3 after the CO2 has been on for a while.

I have seen pearling in my non-CO2 tank when the afternoon sun lights the tank for a few hours.

CO2 isn't everything.

Bill
 

jazzlvr123

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co2 isn't everything, pearling just means your plants are growing and releasing oxygen as a by-product IMO pearls are a great indicator of a healthy tank. If my plants aren't pearling by at least 3 hours after the photo period has started I know something is wrong in my tank and asses the problem accordingly. however since i have started my new setup I have yet to undergo a photo period without seeing pearls everywhere after 3 hours a 5 hour photo period is all my tank needs. If you have good surface agitation via flow you will increase the amount of O2 in your tanks water which subsequently makes the plants more apt to produce bubbles.
 

helgymatt

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I agree completely. I have also seen pearling in non-CO2 tanks I have setup. BUT, pearling is nowhere near what I have in my CO2 tank with good light and ferts.

The poster was asking what it takes to get pearling and I was simply stating what gets the plants to pearl "the most" for me. :)

Also, steveD mentioned that he gets more pearling after a waterchange. Someone correct me if I'm wrong, but isn't this because the tap water will be high in CO2 compared to the tank and cause the plants to photosynthesise more for a short period? I also see this in my tanks.

Also, the idea that a high fish load will prevent pearling may have some validity, but I think in a highly planted tank that is growing well, this would not have much of an effect. Also, I hope someone can comment further about this.
 

Tom Barr

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aquabillpers;30808 said:
Is their a relationship between the amount of O2 already in the water and "pearling"?

It used to be said that pearling would only occur when the water contained all of the O2 that it could hold, but I think that is no longer considered accurate.

Bill

No, not really.
It's just relative to the production of O2, or, the rate of plant growth.
O2 production = plant growth.
It has little to do with saturation.
Localized levels of O2 can hit 200%, while the water elsewhere in a weed mat will be 90%. Both locations can and do pearl.........

At high plant growth rates, obviously the levels will go over 100%, the higher the rate, the more pearling you see, but this has little to do with saturation, merely a correlation with growth, not really to do with 100% or more saturation at ambient.

Ambient saturation vs the maximum that can be dissolved are quite different concepts that do seem to get confused unless explicitly stated.

While much over 2-3ppm is considered beyond 100% saturation from ambient for CO2, we know we can add a lot more before you reach the point where you cannot dissolve more in the water. Likewise, for O2, however it's not nearly as soluble, but you can get a lot more than say 20ppm in there if you wanted to, it will degas, but if you add it faster than it degases, just like CO2, you can get more in there.

Regards,
Tom Barr
 

aaronnorth

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Thanks for all the replies. I do get pearling in my Aquarium :) but was just curious as to what caused it.

So it can be caused by O2 saturation (usually water change) or by injecting a high enough rate of CO2. Plants take CO2 in, use the carbon then release the O2.
 

ccLansman

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I have to agree with the above posters who say pearling is directly related to co2 concentrations and decent fert amounts. The light only seems to factor the speed at which the bubbles are released. If you want to see it in action plants are fairly responsive to light intensity changes. If you have the ability to vary the lights in your tank try turning on about half the light and wait for the pearling to start (about midday or mid afternoon for me). Now turn on all the lights and give the plants about 5 mins you should see a dramatic increase in bubble production and overall pearling. I have given up on drop checkers since mine is always yellow and all my fish are fine when co2 is cranked up. So IMO forget what the drop checker says, look at what the plants are saying.
Another fact that is very important is good flow. I have a 60gal with two can filters, 1 koralia1 and a power head to get good circulation going. Before this I had two spray bars for my cans instead of regular outlet nozzles. With the spray bars I was lucky to get any pearling even with co2 streaming out of my bubble counter so fast that I was not able to count it. With the new heads I get much better flow and now have my co2 turned down to about 6bps and get even better results then the spray bars offered. Hope this helps! (Don’t give up, I had a frustrating time trying to get everything just right myself.)
 

helgymatt

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Equation for photosynthesis is:

6 CO2 + 12 H2O + photons → C6H12O6 + 6 O2 + 6 H2O
carbon dioxide + water + light energy → glucose + oxygen + water

CO2 and light are going to drive O2 production.

Not very related to O2 saturation as Tom said
 

Chiya

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Jun 23, 2008
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Hi all,

Just curious, we know photosynthesis causes pearling. BUT, is it a good sign of healthy plant growth?

My plants do produce little O2 bubbles, which float upwards and dissolve almost immediately.

I've not seen pearling in my tanks for as long as I had them.

There was a thread regarding pearling.

http://www.barrreport.com/co2-aquatic-plant-fertilization/4582-pearling-conditions.html

There was mention that pearling happens when plants are overworked.

Hence it makes sense if pearling happens when there's a saturation of O2 in the water.
Plants are overworked, producing more O2 than normal.
O2 production > degas rate + respiration
O2 reaches a saturation level in the water. O2 is unable to dissolve into the water fast enough.
**Pearling** occurs.

Comments??

Regards,
Ryan
 

helgymatt

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Chiya;30892 said:
Hi all,

Just curious, we know photosynthesis causes pearling. BUT, is it a good sign of healthy plant growth?

My plants do produce little O2 bubbles, which float upwards and dissolve almost immediately.

I've not seen pearling in my tanks for as long as I had them.

There was a thread regarding pearling.

http://www.barrreport.com/co2-aquatic-plant-fertilization/4582-pearling-conditions.html

There was mention that pearling happens when plants are overworked.

Hence it makes sense if pearling happens when there's a saturation of O2 in the water.
Plants are overworked, producing more O2 than normal.
O2 production > degas rate + respiration
O2 reaches a saturation level in the water. O2 is unable to dissolve into the water fast enough.
**Pearling** occurs.

Comments??

Regards,
Ryan

If you plants are producing little O2 bubbles then you have pearling!

Overworked...dought it. Think about this. On a cloudy day your garden plants are not going to grow much, but on a bright sunny day your plants are going to grow. Same is true in a tank. If I turn the lights down, no pearling, turn them up, pearling. Pearling is just a sign that the plants are producing oxygen, a product of photosynthesis! In order for plants to grow, photosynthesis must be at a faster rate than respiration. How possilby could a plant be overworked because of too much photosynthesis? When my plants pearl the most, they grow the most, if they are overworked/stressed, it sure isn't obvious to me!