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Adding phosphate (is this nuts?)
Bless me for I have sinned. It's been three months since I've posted on
APD...
Steve Dixon wrote:
> Many of us strive to maintain phosphate-limited conditions in our
> planted aquaria. This is one of our basic algae control strategies. Can
> there be such a thing as having too little phosphate?
Steve and I are members of the same local aquatic plant group in San
Francisco, as are Tom Barr and Dave Gomberg. About 1-1/2 months ago I was
complaining to each of these experts separately about my strange staghorn
algae, slow plant growth, etc. Dave pointed to PO4 as the limiting factor
right off but I dismissed this idea - I couldn't believe that adding
phosphate could possibly make an improvement. After all, I'd spent months
learning how to limit my tank with it, and seen the improvements from such a
strategy.
I had been maintaining near-ideal conditions for a long time in my CO2
injected 50g (110w PC fluorecents): 6.6pH 4.0dKH, 6.0dGH, trace ("some")
Fe, 10ppm NO3, and I feed my moderate-to-heavy fishload sparingly. I was
watching all of the macro-nutrients individually and together, and was using
TMG and Seachem Equilibrium regularly. I couldn't figure out why the tank
wasn't taking off, especially since it had really been going great-guns for
about two months. That was the clue, and I missed it.
> I'm using 1/10 gram amounts of potassium monobasic phosphate with
> quite surprising results (beautiful, is actually the right word for it)
under a
> variety of high growth conditions. I have a fairly good feel for what
this
> supplement is doing to nitrate levels (driving them down, as one would
> expect).
I borrowed a lifetime supply (thimblefull) of the stuff from Steve about a
month ago and started experimenting, watching NO3 and PO4 levels carefully
with Lamotte test kits. It turns out that with my plants, fishload and
feeding schedule I can use about 1/8 gram PO4 and 1/4 tsp (haven't weighed
it) KNO3 every two to three days. That proportion is critical. Too much
PO4 and I see GSA and BBA, too little and growth stops almost immediately
and staghorn algae takes over. I should point out that algae intrusion is
dramatic in those cases, literally taking over the tank in a single 10-hour
photoperiod.
Plant growth has been phenomenal lately. I live with the remnants of a few
crashes - GSA that won't go leave the rocks and Anubias leaves (but is not
encroaching - even my glass remains clearer than it used to), dying BBA on
my driftwood, and hair algae on my substrate (time to get some live-bearers
- I can't figure out why my C. japonica don't eat it).
Not for the faint of heart. I shot some new pics yestyerday and will be
posting them on http://www.rubinworld.com/aquarium.htm over the weekend. I
think I'm probably a better aquarist than I am a photographer. BTW, there's
also a page of photos I took of Steve's tanks at the same location.
--------------------------------
michael rubin
mrubin at visa_com
1(650) 432-4685