I have noticed that several people here add several drops of fertilizer 
everyday to their tanks.  Does anyone have any suggestions on a brand?  
Currently I add the tablets.  Do I need liquid also?

To describe my tank......... I have 4-48" florescent tubes that I leave 
on for 11 hours.  Comparing my plants to the diagrams in the books, my 
plants all seem to be tall and "lanky" and don't have the rich dark 
green look(very slight greenish-yellow).  The leaves at the bottoms 
have all fallen off, yet the tops look nice. Also about mid point on 
some where the leave have fallen off, roots have started to grow.  I 
rarely clean the bottom of the tank with all the plants growing, but 
change 25-30% the water about every 10-12 days which keeps the tank 
very clean. I don't have any problem with algae above the "gravel 
line".  Beneath the gravel there is a dark algae growing which I can 
see looking though the glass on the side where air bubbles also form in 
the gravel...should I worry about this?  I have noticed it growing for 
several months but has never "bloomed" and says below the gravel.   I 
have the following plants:

Cabomba caroliniana
Bacopa caroliniana
Synnema triflorum
Echinodorus tenellus
Amazon swords
something like Telanthera lilacina but green...not red

My main desire is to have thicker looking plants on the greener side.  
Any suggestions would be helpful.  Thanks!