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Re: Funky algae



>It is dark olive-green in color, and looks like long, narrow 
>bubbles or tubes formed around the leaves of my plants, 
>especially those with very small or needle-like ones.  
>It almost looks like jellyfish tissue.  I can remove nearly 
>all of it from the tank, and a few days later it looks like 
>I did nothing.  It breaks up easily and has almost a stick 
>consistencey.  Possibly a cyanobacteria?  As for water
>quality, I do weekly water changes, which has led to phosphate
>problems in the past (high phosphates in the tap water), so this 
>could be an issue.  My nitrate readings have always been 
>virtually zero, so I know this isn't the problem.

Sounds like blue-green algae.  These organisms have the ability to fix
atmospheric nitrogen, so a low N/high P aquarium actually favors the
growth of blue-greens over other algae and plants.  I suggest you
continue removing as much as you can, and start adding nitrate (KNO3
would be best).  If you don't have any fast-growing plants, you should
probably add some to help eliminate excess phosphate.  Your tank is
nitrogen-limited, and favors the acculmulation of phosphate.  Other
nutrients (e.g., K, Fe, etc.) may also be limiting.  Do you add any
supplements?

I'm willing to bet your tank has higher P than your tap water, because
of the phosphate you have been adding via fish food.  If you have an
accurate test kit, you may want to compare the phosphate in your tap
water with your aquarium water.  If the tap is less, it is advantageous
for you to do regular tap water changes.  It's the quality of your
aquarium water, not your tap water, that matters.

Regards,

Mark
in soggy Austin, TX