What size tank do you have them in?
Betta are aggressive and territorial fish. They often do not get along with other fish, unless they are in a very large tank and have lots of places to hide. Even then, some betta still will not get along with other fish. If your betta is chasing your goldfish, then he is probably being territorial. I would suggest separating the fish (putting one in another tank) because the betta is likely stressing out the goldfish. For information on betta care, see
http://healthybetta.com/.
Also, I'm not sure if you are aware or not, but goldfish require A LOT of space (much more than a betta). Department stores often sell little bowls for goldfish, but it is actually recommended that you allow 10 gallons of tank space for each goldfish because they can grow quite large and they are quite dirty. For more information on goldfish, see
http://www.geocities.com/Tokyo/4468/ and
http://www.koitime.com/goldfishguy/index.htm
Sorry if you know most of this already, but I am just trying to cover all of the bases. Hope this helps.
