duplaplant tabs. and MH

Hi all,
	I'm in the process of setting up some new tanks and
have just bought some laterite and duplaplant 24 drops, 'coz
you people keep sayin' how good they all are.  The laterite 
came with 10 duplaplant tablets, which is for a 200L pack, 
but no instructions as to what to do with them.  I have 
looked through the aquatic-plant archives and found that the
tabs. need to be added at setup and at water changes.  Is 
this correct?  Now if I get 10 for 200L that must mean I 
need to use one tablet per 20L each water change!  Hoiw am I 
going so far?  I therefore will need to buy more duplaplant
tablets, will I not?  I don't know what you guys (and gals)
pay for it in the states but geez it is expensive over here!

	My second question is regarding MH lighting.  In the
near future I will be setting up a 4'x2'x2' planted tank for
dwarf cichlids.  I intend to use MH lighting, probably 
2x250W, is this too much?  I've seen a lot of talk about the
kelvin rating for various bulbs ranging between 5000K-20000K.
Is bigger better?  If the higher rating bulbs are more 
expensive, but better, is it justified to spend the extra

Thanks very much for any assisstance you can give me. 

Simon Mann