My 29 Gallons

I am looking for advice concerning my 29 gallon tank.  I set it up about a
year ago and am not satisfied with the way it looks.  I consider it my
"learning" or "practice" tank  and will use the knowledge gained from
keeping this tank, along with advice from this list and other research
material in setting up a 55 gallon planted Discus tank in the future.  All
comments and suggestions are welcome.  Specifically, what I am doing wrong,
what I am doing right, and what could I be doing better.  Also, any
suggestions on plants that would do well are welcome.  The tank conditions
are as follows:

TANK SETUP:  29 g / 110 liter.  AquaClear 500 w/2 sponges.  Visa-Therm
heater.  Substrate:  3" / 7.6cm  brown  aquarium gravel approx. .25" -
.375" / .6cm - .95cm  No additives.  Lights:  24" shoplite fixture with
two 20w bulb fixtures.  One cool white bulb and one Vitalite.  DIY Yeast
CO2 bubbler  with bubbles going into the intake of the AquaClear.  Bubbles
at 1/sec.  1 Piece driftwood, 2 lava rocks.

TANK WATER CONDITIONS:  Temp:  23c / 74F;  PH:  6.5 - 6.8;  KH:  2; GH:  6;
 Fe:  0.1 - 0.5mg/l ;  PO3/4:  5.0 - 10.0 (ouch!);  Ammonia:  0;  Nitrite: 
0; Nitrate: 20ppm 

TAP WATER CONDITIONS:  PH:  7.2;  KH:  2;  GH: 4;  PO3/4:  .5ppm;  Nitrate:

FISH:  4 - Angels (3.8cm /  1.5" each); 4 - Red-Eye Tetras (1.3cm / .5"
each); 2 - Cory Cats (2.5cm / 1" each);   1 - Bristle Nose Pleco (Ancistrus
dolichopterus?) (5cm / 2"); 1 - Loach (6cm / 2.5"); 2 - Otocinclus vittatus
(2.5mc / 1" each)

PLANTS:  Ludwiga repens, Hygrophila polysperma, Hygorphila difformis,
Vallisneria spiralis, Sagittaria sbulata, unidentified Hygro (labeled
Tropical Hygro).

MAINTENANCE:  Weekly 10 gallon water change.  One drop a day of Kent
freshwater plant micronutrient supplement with iron (I read somewhere that
this product could be used as a daily dose).   I clean the filter and
sponge once per month.

PROBLEMS:   The bottom 2/3's of the Ludwiga is completely bare of leaves,
the upper portion looks great.  The Hygrophila difformis does not grow very
well.  Vallisneria looks great.  The Sagittari is not growing very well at
all.  The Hygro poly and Tropical Hygro are going like wild.  I have lots
of green spot algae on the glass which I clean once a week.  I have an
unknown type of algae on all the plants which looks black and starts on the
edge of the leaves and eventually covers the leaf.

John Riggs
Virginia Beach