I was at my LFS today and was looking at the green sevrums. They are about 2-3" long but green sevrums are pretty tall too. Well anyway I have 3 o's 8-9" long in 160 gallon tank with no tankmates. Firstly could they eat my new friends? Secondly how could I introduce the fish so my O's don't get excited and think they are getting fed. I was thinking I could feed them until they are full and after a water change when the O's are a little less bold add the sevrums. Any other thoughts?

you could move the contents of your tank around. this will also give the oscars something to think about and explore. how many are you thinking of adding. 160g is a good size for 3 o's and makes life easy,if you add too many your work load will increase.

i agreee with marcus. move things around and make sure the smaller fish have a few places to hide until your osccars get used to the idea of sharing their tank

I don't think adding new smaller moving object in the tank is a good idea. Oscar is also a territorial fish, meaning they usually protect/defend their area and get small intruders or drive away same size intruders. Eventually, your sevrum will become meals of your oscar.

Even if they are newly feed, they still grabbed any moving object and spew out later if they can not gulp them totally.

your sevrum may become food and this is something you have thought about and it maybe a risk you will dicide to take.?? i have had 6" clowns with 12" oscars and could have been food but were never eaten.?? how aggresive are your oscars could be something to keep in mind. if you add them let us know how things go.

I find when adding new fish i usually feed my guys first, then do a nice big waterchange previous day, then when i get different fish, rearrange tank, float bag for atleast an hour,,letting them get used to seeing the fish<also see what the oscars do in this time,,
I personally only like to keep one species of cichlid in a tank, as i have had alot of problems with cichlids in the past, when i was new to the cihlid world,,

i had a vieja bifa who killed a green severum,green terror,beat living hell out my two oscars<got photo evidence to prove all this>and also beat hell out of a female jack dempsey,,,,didnt touch the manga<hehe would you,,

so its left me sceptical about keeping different varietys together, dither fish on the other hand do not seem to bother the oscars