Do you vacuum? Do you peat/soil?

I have two basic questions to which I have been unable to find complete 
answers in the FAQ or in any of my reference books.  I hope you can 
answer them for me.  I have a 30g long, with just one 20W Lifeguard 
Biolume fluorescent bulb.  My Java Fern has flourished, and I recently 
purchased Java Moss and a beautiful little specimen of a. nana.  I only 
have a layer of bigger-sized gravel for substrate.  I use a Whisper 2 
power filter.  There are 12 neon tetras, 4 black neon tetras, 2 
ottocincluses, 1 angel, 3 albino cats, 9 zebra danios, and 1 fluorescent cat.

My questions are related:
1) Should I vacuum the substrate during my weekly 5g water changes?  When 
I used to have only the Java Fern (and I had so much that I simply 
planted it in the gravel after it overgrew the bogwood) I vacuumed 
everywhere but where it was growing.  Now that most of the bottom is 
covered with plants (2 amazon swords that could look better are also in 
there), what do I do?  Just let the mulm stay in the bottom?

2) Should I mix into the gravel something else in addition to the 
occasional tablet of Tetra Crypta Hydro?  If so, do I need to remove all 
the water, fish, and plants temporarily?  My books say that a. nana likes 
a "rich substrate."

Thank you for your advice.