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Phosphate limited tank??

Hello, I have read a number of letters regarding growth of plants being
limited due to lack of phosphates with great interest.  I have an 87 gal
heavily planted medium fish load tank.
After have a bout with BBA which I solved by water changes (I had high
phosphates) and using phosp-sorb for a month and a hydrogen peroxide
treatment I basically got rid of all the BBA and only have some spot
algae and the occasional bout of green water (explained later).

My problem is no I never have ANY phosphates in the water... I always
read 0 (no P in tap water).  Now while there is no algae growth other
than spot algae the plant growth is nothing special. I'm not using the
phosp-sorb anymore and the fish/food doesn't seem to add enough P.

My tank is 87 gal, 2x 175W MH lights, fertilize with PMDD, KH 8, GH 4,
PH 6.8, NO3 10ppm , PO4 0, Fe .1, and DIY CO2 injection.
My problem is that the N increases over time.  I had hoped that the
plants good growth would keep the N down but it seems with no Phosphates
they don't grow fast enough and the N rises.
Now when the N hits a certain level (usually 40ppm) I get a green water
bloom.  I can do a water change to keep the N down but then my water
chemistry is blown (we have hard water here).

So I'm think of trying the following.. (here is where I need the hints!)

- Starting to use TMG fert.  Thinking maybe I'm missing some micro
nutrients although I had hoped they would be in the tap water (no growth
increase when doing a water change)

- Using Jobe's sticks in the substrate. Question! The Jobe stick
recommended is LOW in Phosphates... since this is where I think the prob
is wouldn't I want low N and high P??
Already have enough N in the water.

- Adding Phosphates directly to the water  while making some sort of
live sacrifice to the fish tank god not to bury me in a tankwide coating
of green furry stuff.

Thanks for your help