You can feed the guppies this:
http://www.petsmart.com/product/index.jsp?productId=2752270
And of course you can buy it at Petsmart.
You can buy your Neon Tetra's this:
http://www.petsmart.com/product/index.jsp?productId=2753186
And of course you can also buy this at Petsmart.
blood worms, brine shrimp. would probably be the best thing to feed fish. thay also eat some celery and greens...well mines do =)
but blood worms and brine shrimp would be the best...