[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Adding phosphate (is this nuts?)

Bless me for I have sinned.  It's been three months since I've posted on
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

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
> 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

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