What causes pearling/ When does it occur?

Thanks

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

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

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.

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

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

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.

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.

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