ChristyLynn wrote:
I haven't tested my water in a while. Actually I only do a water change
once a month. I have a little bit of algae but not much. I just noticed
some red algae on the glass, which I did not have before, so I decided to do
a water test. Here are my results. Unless I am wrong, they seem very good.

Nitrate 0ppm
Ammonia 0ppm
pH 6.0
KH less than 53

I have a 10 gallon aquarium with 1 larger red cap oranda, 1 cherry barb, 6
small half clear light yellow fish, they almost look like they are in a
tetra family but I don't recall their name, I also have a pleco, and the one
apple snail which its health is questionable.

I have had all of these fish together for over 3 years. So, I am just now
wondering why the reddish algae when I have not done anything different over
these years.

A ph of 6 is way to low for your Oranda. You also have fish with
different requirements, such as water conditions and feeding together.
Tetras have faster metabolism than goldfish and thus have different
feeding requirements. Tetras also prefer softer water, such as you
have, but not the Oranda.
As noted on your other post, I recommend a KH of 80 ppm for the calcium
requirements of your snail AND now your goldfish too. The Tetras and
barbs also require calcium (all fish do, even discus- if not more so
with discus from my experience and reading Marc Weiss literature).
I would read this URL about calcium and KH:
http://kh-aquarium.blogspot.com/

There is more information here about feeding and other aquarium
requirements, including a link to NetMax's web site with even more
great information:
http://aquarium-info.blogspot.com/


As for the red algae, this sounds like cyanobacteria, which is not even
an algae. I usually see this in sal****er. This is NOT desirable and
improving your water conditions will help with eradication of this. (A
good Redox Potential helps here). Here is a site with information about
red slime algae:
http://saltaquarium.about.com/cs/mic...a/aa092800.htm

Carl