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Discussion Starter #1
I try to understand better (if it is possible at all) what prevents or inhibits algae growth in well planted high tech tanks. One question keeps bothering me.

Is there a basic difference in tolerance of high oxygen levels between vascular water plants and most algae?

When we look in a well planted and fertilized tank with high light we see the many bubbles coming out of the vascular plants, i.e. they are capable of releasing oxygen as gas even at almost complete oxygen saturation in the water. I guess that most algae cannot do this, since they do not have gaseous oxygen. Otherwise they would all float on top of the water. If they cannot do this, they obviously have to release dissolved oxygen against the high saturation levels in the water. It may also lead to higher internal oxygen levels compared to vascular plants which negatively affects their Rubisco activity. May this be a reason why such tanks suffer less from algae problems or do I miss something here? :confused:
 

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I don't think our aquariums ever achieve oxygen saturation. Pearling doesn't require that. Some algae also will pearl - GDA for example, late in its life cycle. So, I doubt that there is a significant relationship between oxygen concentration in the water and algae growth.

If I am wrong it would only be the 5,629th time.
 

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Kasselmann, a German water plant specialist, refers in her book (1995) to 70 - 130% oxygen saturation in well planted dutch tanks. This is the only source I found. I read other threads that mention pearling at lower concentrations especially with low water movement leading to locally high concentrations over the leaves. But I do not know how much water movement is required to overcome this. Maybe there are other studies that report lower values? I would still be interested whether algae can generally cope less well with higher oxygen levels. I did not find much about it. But maybe it is not important as you mentioned. This would just add to my way higher count of being wrong ;)
 

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It's my opinion--I'm just a hobbyist, not a scientist--that oxygen plays a huge role in the health of planted aquariums, but does not affect algae directly. We tend to think of fish being the most needy of oxygen, and while that's sometimes the case, they aren't the only living organisms that require an abundance of oxygen. Bacteria often require larger amounts of oxygen than fish do in order to perform efficiently. If the bacteria can't do their job, then everything else in the tank suffers. The result of that is algae. The nastiest cases of algae seem to appear when the biofilter is limited and weak, which lead to eutrophic conditions. A tank can start out well because a strong biofilter isn't really needed, but as the tank matures, the larger the bacterial colonies become, and the more influence they have upon the tank. Long term success depends upon an efficient biofilter.

On the other hand, too many bacteria can hurt a tank as well. If the bacterial colonies become too large, they can literally suck all of the oxygen out of the water, suffocating fish. This is generally what happens when filters get too dirty and substrates become too nasty. This is why proper tank maintenance is crucial. In higher tech tanks, you generally see people performing regular maintenance which could be indicative of lesser algae issues than from lower tech tanks (excluding 'self-imposed' algae issues such as nutrient/lighting problems). Some algaes I've attibuted to oxygen/biofilter issues are green fuzz and BGA in some cases.
 

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Yes, I heard about the importance of algae. I think they are sometimes responsible for "dead zones" (oxygen-free areas) in the ocean and lakes when dead algae are processed. So, I guess it would play a large role in tanks if you have much material that bacteria feed on.
 
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