Can eels tell if a fish is weak?

[francesux]

The other dya my friend brought over a goldfish he nlonger wanted because it was terrorizing the other fish in his tank. We thought we could put it in with my oscars and they would eat it. After the fish swam around with y oscars getting terrorized and bitten but not eaten we thought we would give it a shot with me eel. This is a snowflake eel in a tank with a bunch of damsels. not 5 seconds after the fish was in the water was its head gone and being devoured by the eel. I could not figure out why the eel ate this fish soo quickly but does not eat the damsels and explanation would be greatly appreciated.

 

[archon]

this post must be a joke? cause last time i checked u said u put a goldfish in with the oscars. that would be freshwater. then you put it in SALTWATER? well... that doesnt answer your question. but anyways this is my thought. say u have a slower fish(goldfish in this example) put it with something that is aggressive, its going to get eaten. the damsels may live because damsels are pretty fast.... try and catch one... they are also aggressive too. just my thought im a newb at this so....
edit: i guess if u just want it to get eatin it would be fine... but im new to this so ive never heard of taking live goldfish and feeding them to saltwater fish.

 

[jag3365]

Yeah most predators, such as eels, can tell when a fish is weaker than the rest. Happens in nature all the time, how lions pick off the slower of a heard, certain insects will feed off the weakest link in their chain. Eels are used to damsels around probably have an almost symbiotic relationship, except when the eel is starved. Just my thoughts.
And archon...goldfish can be put in saltwater and freshwater. They are like guppies in a way that they can survive in both conditions. Althought not as well in SW. There are some people who feed goldfish to SW fish if they are having trouble feeding them other ways. Sometimes it's the only way to get them to start eating if they're new to a tank. However most peopel do not like this as goldfish are not very good for SW, and don't offer very good nutrition. HTH