Yes, you can use anything that would rot in a tank to get the cycle going. Old-school methods used -dead- fish carcasses which is how the whole "cycle with fish" began. But I like raw chicken on a sting, or a nice hunk of cocktail shrimp. You can also use pure ammonia if you can find it on the market.
Old school cycle methods have always been throw in a few fish, what lives, lives, what dies is what is contributing to the cycle. Fish used in old school were feeder goldfish or guppies. THIS IS NOT A GOOD IDEA! Feeder fish are not kept in the best of condtions at the LFS and carry parasites. Thus you will be introducting parasites to your tank that could make your ornamentals sick. Also, goldfish are non-tropical so should not be in a heated tank or mixed with tropical species. And then you would have to find a home for the guppies...
The method I would usually recommened to people wanted to do a with-fish cycle is only add about 2-4 fish every two weeks, doing a 10% water change once a week. EXPECT DEATHS with this method. Some fish can handle an unbalnced tank better than others. Most impatient folk don't want the "unpretty" fish that are relatively hearty, but want the delicate ornamentals right way. The delicates definately cannot be used to cycle. BEING SLOW AND PATIENT is the key. You want to add fish to add their waste, but you don't want to add so many fish that they end up dead from their own organic matter! Think of it as swimming in a public kiddy pool without a filter. This method is relying on the dilution volume of your tank to keep the resulting ammonia spikes below toxic levels. Bacteria does not happen over-night and takes about two weeks to match the bioload in the tank. You will only have enough bacteria to convert ammonia from those fish in your tank. Adding any addtional fish will create additional and larger spikes.
Fishless cycles allow you to reach toxic ammonia spikes quickly, which will further encourage bacteria growth as well as give you a bacteria population that will support a full bioload of fish without additional spikes. Test kits are a heck of a lot cheaper than having to purchase fish all the time. When doing a fishless cycle, ammonia levels should spike >5ppm then drop back down to zero, nitrites will peak >5ppm then drop back down to zero, and your nitrates should then begin to rise. Water changes are what keep nitrates in control (filters do not remove nitrates) and nitrate levels in fish tanks should not exceed 5ppm. Once you start seeing nitrates in your tank, commense with weekly 20% water changes and add your fish.
Whatever method you choose to use, both require patience. If you just can't wait to put fish in your tank, please realize that it is not the fault of the LFS if they die, so don't harass their employees.
~~Colesea
