larvae in tank


I'm having problem with some kind of green larvae/worm in my tank. It is 
about 1cm long and 1.5mm thick and cuts up my leaves to make themselves 
a home each. I already removed 7 of them. Anybody guess what it is and 
the solution to this problem?

One of my stem plant species just melt and I have to remove all of them. 
My other stem plant may be having this problem soon. A few of their stem 
has turned brown. Is this because of not having enough light or cause by 
the worms above?

My two Black Mollies has been pecking(?) at the floating plants' root 
and my brown coloured stem plant. This has broken the stem plant many 
times and those fur-like roots. Good thing is the stem plants keep 
coming up with new branches. I thought Mollies don't hurt plants.

Reason I do not have any names for the plants is because I have not 
identified any of my plants yet except for the Japanese Rush.

50 gal plant tank with 2 Black Mollies and 4 Zebra Danios 18 days into 
cycling, if it ever cycle. My two previous water test shows 0 for 
Ammonia, nitrite and nitrate. The only change is PH from 6.7 to 6.0.

Thanks. rgds..kbkoh