Like anything it depends on the individual. 200 clams should last a while tho' you may want to open them to start with for your octi, not all can get through the shells, it's a learned behaviour for many octis.
Regarding variety.............I'd go for some, add in some shrimps or crabs. Also not all octis will eat clams Squidgy won't...he's a crustacean lover!
on the topic of food does any 1 use the shrimp from shrimpstuff.com to feed there octo. being semi land locked i have a hard time finding in expesive food sources as the pet stores in mt area(includeing petco) arnt carying fiddlers anymore. would a 10gal be a large enough feeder to sustain the smallest order u can get from them? any other info would also b apreciated.
Having a seperate tank for food is good as you don't want any of your live food accidently dying in your main tank and fouling up the water affecting your octo etc.
Also you don't want to many feeder animals in your tank, it could stress out your octo or even harrass it. With food all over the place, your octo will be able to eat anytime of the day, not only when you're around. And trust me, watching cephs feed is fun, and a great way to interact with your ceph