Plant Fertilizer Question:

[torch89]

I currently have two planted tanks.  One is a 20 gallon tank done with Flourite, and the other a 10 gallon with fake rock.  Should I use fertilizer on top of the Flourite in the 20 gallon tank, and if so, how often should it be added?  In the other 10 gallon tank with fake rock, how often should I add fertilizer to the water?  Answers much appreciated.   

[BigDaddy]

Depends on how much light you have over each tank and what kind.

[torch89]

Specs are:
For my 20 gallon with Flourite substrate, I am using a GE Plant & Aquarium Bright Stik Grow & Sho.  It is a T12 Bulb, 33 watts, 470 Lumens, Color Temp 3050 K, Color rendering Index of 90.
For my 10 gallon with fake gravel I am using 2 bulbs.  First one is an Eclipes compact fluorescent 10 watt, 5100K natural daylight bulb.  The other one is a Penn Plax, aquari-lux "PG" aquarium light plant growth bulb, 15 watt, yellow cast.  I tend to switch these two bulbs back and forth on this aquarium. 
As for CO2, I am not using any at this point on either aquariums.  Any suggestions regarding if I need fertilizer and how often to use for both tanks would be greatly appreciated. 
Thank you
Cheryl

[BigDaddy]

Both of your tanks are essentially low light tanks.

Unless you have some fast growing stem plants like anachris, hornwort or hygro in your tanks, you will do fine with what is already present in your water.

If you notice a bit of yellowing... then you might want to add a little bit liquid fert from Flourish, Kent or Red Sea.  Use the recommended dosage once after your waterchange.