I leave them completely alone; no fertilization at all.  I do throw in a 
fruit fly now and then to the leaves.
I seal the bowl with saran wrap and a rubber band.  This is not a 
high-tech operation, as anyone who has seen my place will attest!
Bob
 /========================================================================\
| Bob Beer         		      \   "A troubled mind                 |
| bbeer@u.washington.edu                \    is a troublemaker."           | 
| http://weber.u.washington.edu/~bbeer    \     - Edna St. Vincent Millay  | 
 \========================================================================/