DO NOT USE feeder goldfish they are oily not very nutritious and constant feed of them causes faty deposits on the liver they also contain very high levels of Thiaminase a destroying hormone.
another issue with goldfish is the presence of a 'spine' in the anterior of the dorsal fin, this can prove problematic if the fish swallows the feeder the wrong way or further issues in the digestive system. goldfish are just not a good feeder (not that feeders in general are that great). if you have to feed feeders, as mentioned above, go with guppies or rosies. i prefer rosies since they seem to be a little less susceptible to ich and the like...although its good to quarantine feeders if you can.
Feeder goldfish farms utilize copper meds in suspension form to combat diseases in the feeders associated with overcrowding. These copper meds are retained by the feeders for long periods after they leave the farms. Most lfs invariably retain all or part of the feeders shipping water when the feeders are loaded into their bins/tanks. And copper does not dissapate from a closed system. -Anne
