Re: Problem Plant Tank

John Lobingier wrote a long description which I'll summarize:

Before increasing lighting levels and adding CO2 injection things
appear to be growing slowly but ok and now some leaves are yellowish,
get pale and drop off despite fertilization with trace nutrients
and potassium. Nitrate levels are measured at 12.5 mg/l. He didn't
say so but it sounds like the tank still is heavily stocked with
Angelfish and presumably are well fed.

The symptoms you describe sound like a deficiency of nitrogen or
potassium. Perhaps the test kit is not giving an accurate reading
of nitrates? You could test it to see what reading it gives for
distilled water or tap water. Distilled water should be zero and
tap water should be much lower than 12.5; if not then the test kit
is giving misleading results. I don't know what all those other
things are in your filter. In my tanks I use only a mechanical
filter pad or nothing at all and I use PMDD every day. I've had
symptoms similar to the ones you described with my high lighting
before using PMDD although I have much less fish than you. It has
made a dramatic difference. Perhaps something chemical in your
filtration system is interfering with the nitrogen test and/or
interfering with the plants ability to get nitrogen somehow.

Steve in Vancouver