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RE: Black algae? or maybe a deficiency

On Wed, 11 Aug 1999, I wrote;

<For the last couple months, I've been battling with what I originally
thought was some kind of black algae.  I've come to the conclusion that it
might be a deficiency rather than algae (although I've been wrong before).
Whatever it is, it only effects the Swords and Java Ferns.  The older leaves
turn black and then start to deteriorate. I don't think it's because of the
light because leaves that are shaded are still effected.  The plants are
growing very well.  The Swords have just bloomed (little white flowers).  I
normally have to trim every week and they bubble like crazy for the last 5-6
hours the lights are on.  Tank parameters are as follows:

72 gallon, been running for almost a year
3" Profile Aquatic Soil substrate with 1" of gravel on top
Inhabitants, 5 adult and 12 juvenile Angels
Pressurized CO2, 2 bubbles/sec.
2-175 watt MH pendants
lights on for 10 hours/day
10% water changes every 3 days
pH 6.6
kH 7
temperature 80f
gH 16
Nitrates 5-10
Phosphates not detectable with a Seachem test kit
1 ml Kent Freshwater Plant Supplement per day
1/8 tsp. Potassium Nitrate added as needed to maintain 5-10 ppm level,
usually every 7-10 days
1/8 tsp. Potassium Chloride every 7 days (recently switched from Potassium
Sulfate, but problem existed way before this)
Jobes Palm and fern sticks added around Swords about every 6 weeks

Not long after things started turning black, I also got some green/gray
furry algae, but it has only grown on a large piece of wood>

Since then, I have discovered the cause, it is algae.  On Fri, 20 Aug 1999,
Roger Miller wrote the following and confirmed my suspicions;

<The light color could be attributed to nitrogen deficiency, but I don't
think it is.  I didn't mention this in my original letter, but I tested
for nitrate before posting the question.  My Wardley nitrate kit indicates
that nitrate is present, but at a level at or just below 10 mg/l - the
lowest color value on its chart.

I have Tetra and Aquarium Pharmaceuticals nitrate tests as well and in the
past I've often used all three when I tested for nitrate.  The Tetra and
Wardley kits agree and the A.P. test never detects nitrate in this tank. I
only ran the Wardley this time.  I recall Roxanne Bitmann tested several
kits and concluded the Wardly was a was a good nitrate test for the price.>

I have always (until recently) used the Wardley's nitrate test, but the LFS
didn't have one the last time mine ran out, so I bought an Aquarium
Pharmaceuticals kit.  After looking back at my records, this is about when
all my troubles started.

I had to add 3 times the usual kno3 to get a reading from the AP kit (I
should have realized then that something was wrong).  Apparently the very
high nitrate levels spawned this algae.  I've been doing water changes every
other day and it's going away, disappearing on the Java Ferns and turning
white on the Swords.

Roger, have you ever gotten a reading from the AP kit?  If so, have you
simultaneously tested with the Wardley kit to determine the error factor?

Bob Ashcraft
Pittsburgh, PA

"My wife told me that if I bought one more aquarium, she was going to leave
me.... I'm sure gonna miss her."