Interesting article on B/G algae and Redox Potential


Junior Poster
Oct 29, 2008
i'm having problems with B/G algae again. my aquarium just doesn't fit the description of one that should have such a problem. i feel there is a cause that is not typical that is evading me.

during my research to try and help eliminate the cause or change my aquariums environment to make it difficult for it to flourish, i came across a couple interesting articles. The one about redox potential seems promising...especially as it relates to cyanobacteria.

Blue Green Algae (Cyanobacteria) in Aquariums

Aquarium Redox Potential; How it relates to proper aquatic health

Aquarium (and Pond) Answers: Blue green algae in aquariums

from reading the article (redox potential)....if i'm not misunderstanding it, there might be a case for combating b/g algae by introducing higher levels of sodium, calcium and magnesium specifically.

wondering if anyone has ever attacked this bacteria from this angle? also interestingly enough there is evidence that even the spectrum of light may play a role....especially the warmer colors in the 4 - 5k range (which is what i use).


Prolific Poster
Jan 10, 2009
i have found in a few instances in my limited experience that cyano does not start to grow directly under my lights but where the lights do not illuminate so well. accordingly to your second article it is mentioned about PAR not being sufficient for higher plant growth. with this i can now understand and adjust my lighting arrangement.
the thoughts about dosing Ca and Mg i have also thought about seperately from this article because of thinking the substrate(calcined clay/peat) i am using is somehow binding these elements at the level where the cyano begins to grow.

Tom Barr

Staff member
Jan 23, 2005
These articles are just speculation and mostly based on reefs in the first article, and the part about "water ionization" is frigging rubbish. That's quackery marketing.

As far as lakes, ponds etc, this is for suspended BGA, there's only one main species we deal with and I've detailed the most about the issue.

None of the articles apply to planted stems however.
Redox is central to wetland soils, much less so to the water column.

Aquatic plants modify and change the Redox in both sediments and water column.
Higher levels are achieved with healthy growing plants, lower when they die or do not do so well.

There is a strong linkage between roots and sediment and redox. good growth = good O2 production = higher Redox.

So do not bother with Redox directly, not that it will solve any BGA in a planted tank anyway, but rather, good general plant growth. This is more a biological issue than a chemical one, the biology will modify the chemical state. Not the other way around.

Tom Barr