Ferts and plant ID

["conrad harkrader" <c_harkrader at charter_net>]

Hey all,

I had a couple of questions.  First, I have this floating 
plant in my 8 gallon, and I have no clue where I got it or 
what it is.  Can anyone ID it?  It's the floating one with 
the circular leaves.  I put a pic at:

http://www.kreegan.net/mystery.JPG

My second question has to do with fertilizers.  I recently 
obtained some Potassium Nitrate, Potassium Sulfate, 
Magensium Sulfate, Potassium Mono Phosphate and Plantex 
CSM+B trace mix.  I mixed them all up seperately.  I know 
how to dose them to achieve "optimal" levels.  What I 
don't know is when/how to redose.  I know the trace is a 
few times a week.  What about the others?  Thanks!

Rich;)