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PMDD Dosage and Algae

We have an on-going problem with fuzzy green algae in our 180 gal and
the battle to control it is beginning to wear me down - a lot,

If I may, let me tell you about our setup and what we're currently doing

- 180 gal tank, 6' x 2' x 2' high
- 360 watts, twelve 36" 30 watt tubes:
    - six Philips Ultralume 5000K, 85 CRI, 2380 lumens (I prefer these
tubes because they brighten the tank noticeably over the others)
    - three Philips Daylight 6500K, 79 CRI, 1950 lumens
    - three Hytron Full Spectrum, 5600K, 91 CRI, 1600 lumens
- tank lit 10.5 hours daily
- Two AquaClear 500s with foam in the media chamber plus foam over
intakes.  After several modifications, plexiglas diverters now direct
25% of the output directly across the surface, and 75% of the output
directly down into the water then to one side with a sloped L-shaped
piece of plexiglas.  Fewer bubbles per second (2-2.5 per sec) are
required to maintain a pH of 6.8-7.0 with this diverter setup over
diverters that sent 100% of output (4-5 per sec) directly over the
- 5 lb CO2 bottle provides continuous CO2 to tank.  CO2 output is split
into two lines using Lee's wooden diffusors which are placed low in the

- several pieces of mopani driftwood and smooth river rock of various
sizes form terraces (with L-shaped plexiglas beneath the gravel holding
it all in place)
- 20% of substrate is Flourite, 80% 1/4" and smaller uncoated gravel
- Seachem Tabs (mainly iron and trace minerals) inserted last week deep
into substrate
- PMDD recipe is:
    - 1 tbsp trace element mix
    - 1 tbsp MgSO4
    - 2 tbsp K2SO4
    - water to make 250 ml

- temp is 78-81 F (this high because of our new zebra plecos)
- pH 6.8-7.0 with CO2 (7.8 without)
- GH 4
- KH 5.5
- nitrate consistently at 4-5 ppm
- phosphate unknown (AqPharm test kits only available here and have
proven _very_ unreliable.  Hach test kit is an unbelievable $420 Can.)
- iron unkown (Sera tests available only here and are difficult to
read.  Hach test kit is $150 Can.)
- ammonia, nitrite 0 ppm

- plants are several species of Echinodoras and a few Alternanthera
reineckii "roseafolia"
- moderate-heavy fish load, fed moderately twice daily

- 40 gal water change daily
- filter foams rinsed weekly in outgoing change water
- intake foams rinsed every other day

This tank was initially setup in April 99.  Within a few weeks, the same
fuzzy green algae we now have, along with tufts of black beard algae,
began to grow on leaves, decorations and glass.  Fertilizer was Flourish
and Flourish Iron, no PMDD.

In late July, due to a persistent bout of gill flukes, the fish were
removed, bathed in potassium permanganate, then housed in hospital
tanks.  The main tank was completely broken down and sterilized.
Two-three weeks prior to the tank breakdown, however, the plants were
removed, bathed in Lime-It to remove all possible remnants of the flukes
and placed in an unlit, filtered 10 gal receiving plenty of ambiant

In late August, the tank was re-established.  By that time, most of the
algae had dissappeared from the affected plants, and the plants (minus
the previously affected and deteriorating leaves) were replanted.  The
180 gal tank cycled quickly using media from the hospital tanks (no
flukes have yet reappeared).

Once the tank was re-established, the fuzzy green algae reappeared
almost instantly and is getting worse as I type.  There are also small
black spots of algae (presumably) on the older leaves as well as a
little on the decoration, but not in quantities like the black beard
algae from the last go around.  Glass cleaned off one day begins to
regrow fuzz the next.

Two weeks ago, the tank's lights were turned off for several days, a
bacteria-based phosphate remover (Acquamarine's Phosphate Eliminator)
was added to the tank.  No water changes were done according to package
instructions.  Algae subsided a little.  When the lights were turned
back on, PMDD in small quantities (2-6 ml daily) was resumed and algae
reaffirmed itself wherever it had died back.  Water changes became more

I currently use PMDD that was mixed 3 weeks ago, plus .5-1 ml of
Flourish daily.  Both are stored in the fridge.

Last week I was doing 40 gal water changes every 2-4 days and adding 2-6
ml PMDD daily with algae growth about the same as it is this week.
Plants are growing, but within a few days, new leaves show signs of
fuzzy green algae already growing on them.  Arghhh!

Nitrate levels are tested daily and, over the past week or so, levels
are consistent at 4-5 ppm.

I suspect that we have an elevated phosphate level, though not so much
phosphate as to cause an outbreak of blue-green and/or black beard

I also suspect that we need more light and we're currently exploring the
possibility of retrofitting our existing 2-tube All Glass hoods to
accomodate 3 tubes and relocating the ballasts to either behind the tank
or in the basement.

I'm also considering adding Jobe's Fern Sticks deep into the substrate
to further boost the Echinodoras' growth, but am afraid to do so because
we have enough algae problems as it is.

Beginning yesterday, I finally had it being Ms Nice Guy (or whatever)
and began dosing large separate amounts of K2SO4 (totalling 50 ml) as
well as larger amounts of PMDD (totalling 13.5 ml).  Plants began to
bubble a little for the first time in months.

Today, every few hours, I've added more PMDD based on how much the
plants bubbled.  At 3:00 pm, I was up to a whopping 75 ml of PMDD for
the day (!!)   More plants are bubbling at this high rate of PMDD, but
so is the algae bubbling.  And I'm _astounded_ that a 180 gal tank
containing only 4" to 9" plants will accept so much PMDD without a
drastic outbreak of green water (accomplished this in May, presumably
due to too much Flourish Iron and no K2SO4 in the tank).

A water sample tested 15 minutes after the last PMDD was added reads .25
ppm one hour later using the Sera test.

I realize the Sera iron test is difficult to read, which may be another
of our problems.  However, at low PMDD daily addition rates, algae is a
problem and no plants bubble.  I doubt that such high dosages of PMDD
are acceptable for our 180 gal tank, but really, I don't know.  Could
most of the iron in the PMDD have oxydized and become unavailable for
plant use and high dosing rates are required to stimulate plant growth?
Or is something else going on that I fail to see?  Or is 75 ml PMDD what
others use in 180 gal tanks???

I'd appreciate any and all comments about our situation, pleeeeeeeease

Thanks very much in advance.
Beverly Wladyka
Edmonton AB Canada