Re: Algae or scum ?

On Wednesday, 15 January 1997, David Soh wrote:

> Started using PMDD (old recipe) about a month ago and since then I had a
> minor outbreak of algae of some kind. I have 2 MH ( a 4300K and a 5500K)
> over a 90 gal. tank with manual CO2 injection. It is dark green and forms a
> film or skin-like that can easily be sucked off with a turkey baster.

Cyanobacteria.  The original PMDD recipe is short on K and NO3 (unless
you're using a UV sterilizer and you're dumping in loads of PMDD in order
to get measurable iron), and you may be nitrogen limited.  Check your
nitrates; if you can't measure them, increase the amount of K2SO4 and
KNO3 in your mix (in roughly equal proportions) until you can.
Cyanobacteria can also show up when you've overdone the trace elements,
or when nitrate levels get too high.  Regular water changes will prevent
Kevin Conlin  Montreal, Canada  "We're Canadians.  We HAVE to be polite"
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