Heteranthera doing poorly

["Carlos Sanchez" <tsunamicarlos at hotmail_com>]

Hello everyone,

   Recently, my Heteranthera has failed to thrive. At one point, I was
growing tons of this plant -- it was growing so fast that I had to
prune it heavily every week. Now, it simply does not grow well at all.
The few stems remaining intact are slowly melting away by turning
yellowish and semi-transparent, then black -- usually after all the new
leaves at the tip of the shoot get trimmed off by a male Boesemani
Rainbowfish with an insatiable appetite. Shoots grow fine in the center
of the hedge, taking off quickly before dying after the rainbowfish "prunes" 
it. I've actually observed the fish several times ripping
the leaves off of the plant. Nearly all stems have been "trimmed."
   Could this Rainbowfish be feeding on the stargrass heavily enough
to prevent it from growing at all? Or am I looking at an unhealthy
plant that is suffering from some nutrient deficiency? I've noticed
that the shoots do try to let out a few sideshoots after the tip dies.
Eventually, though, the entire stem succumbs and melts away/turns black.

Conditions:

55 gallon
Light: Too much. 3.75 w/gallon PC. Still like it though. :)
CO2: 30-35 ppm
NO3: 10-5 ppm. I add more whenever I see it get at 5 ppm or lower. (AP
test kit, test nearly every day now)
Kent Plant Supp.: 10 mL after every 50% weekly water change. Add
5 mL on the third day after the water change, and 5 more mL two
days after that.
K+: 2 mL Flourish K every day.
PO4: ? I add 7 drops of Schultz African Violet every time I add NO3
(which is about twice a week).
All other plants (Hydrotriche, Hottonia, R. wallichii & macrandra,
B. caroliniana, B. aubertii, H. micranthemoides, Lud. repens, Lobelia
doing very well now and growing out nicely). Mic. umbrosum just
recovering from a recent meltdown after a green water problem in
late June. Water is crystal clear now. No algae at all now except
for some cyano on the oldest leaves of some plants (starting to fade away). 
Mic. umbrosum growing slowly now with small leaves, but if it
grows like H. micranthemoides (which also slowly recovered) it should
grow like a weed by the beginning of next month...
Fish: 1 large angelfish, 9 cardinals, 1 rummy nose, 1 Cory. metae, 1 blue 
ram, 3 boesmani rainbowfish, 5 otocinclus. All fed daily in the
morning.

I think that's all.

Thank you for your attention,

Carlos

_________________________________________________________________
Send and receive Hotmail on your mobile device: http://mobile.msn.com