Green Water Bloom Cleared

This is a followup to my post describing problems I was having with a green 
water algae bloom.  My water has been crystal clear for a week now after 
doing the following:

    o reducing daylight time from 12 hours to 8 hours, and removing one
      Vitalite tube (total now 2 Tritons, 1 Vitalite)

    o performing about six 50% water changes over a 1.5 week period

    o after all the water changes, replacing the 2 month old activated
      charcoal filter bag in my AquaClear 300 power filter with two fresh 
      bags (one on top of the other)

I still have a bit of green algae on the tank glass in places that are hard 
to reach for my SAE's (these patches are getting smaller), and some long 
(several inches) threadlike algae strands which grow slowly and are fairly 
easy to remove by hand on my Java Moss and driftwood.  

I thought I had red algae on the underside of some old, damaged Java Fern 
leaves.  There were tiny little leaves growing directly on the opposite side
of the 'red algae' though, so it may have been small roots as the fern 
attempted to reproduce.  At any rate, I cut the old leaves off and disposed 
of them.  I haven't seen any of these roots/red algae since.

Nitr*tes have stayed unmeasurable this week with no water changes, so I assume 
the plants are now consuming them as fast as they are produced (when I had my 
green water bloom they were at 3.0 ppm and dropped to 0).  Plant growth (and 
O2 bubble production) has slowed down noticeably though, so I am going to try 
re-introducing the fourth light next week.

Next I'm going to slowly start adding Dupla drops while keeping an eye on
Fe ppm and algae.  I may also try only using the activated charcoal filter
bags in my powerfilter one day a week, so the Dupla drop elements I'm 
adding don't get immediately filtered out of the water.  What do the 'old 
hands' on the list recommend: constant activated charcoal filtration, 
occasional, or never?

Also, I now have a few pond snails.  Do these guys eat plants or not, I've 
read mixed reviews.   Mine stay almost exclusively on the tank glass, 
driftwood, and gravel.  Except for the tiny newly hatched (?) ones, I never 
even see them on the plants.  I don't have any broad leafed plants (unless
you count the a. nana) perhaps those are the type they destroy?

Tank details below.

  38G (36x12x18)  | pH:    6.9 (morning)        | Anubias nana
  glass top       |        7.1 (evening)        | Crypt. balansae
  2x30W Triton    | CO2:  15 ppm (morning)      | Ludwigia repens
  1x30W Vitalite  |        9 ppm (evening)      | Hygro. poly.
  AquaClear 300   | KH:    4.0 dH (+2.5,b-soda) | 'Java Fern'
  Dupla Laterite  | GH:    40 ppm (slowly drops)| 'Java Moss'
  DIY Yeast CO2   | Temp:  80-82 F              | E. tenellus
  2 pc. driftwd   | Amm-N: Unmeasurable         |
  3" small gravel | NO3:   Unmeasurable         | Three 3" SAE's
Steven Hicks,            ILX Systems                  212-720-3148
steveh at ilx_com           111 Fulton Street            212-312-2983 (fax)
                         New York, NY  10038