It's really hard!! Seriously, anyone who has read about fish realizes how much work you have to put into it. You have to read a lot and just research about what fish work.
It might work now, but I promise it won't be for long..
And man, don't feel bad. Most people on here have gone through the same stuff. But making good decisions is what separates good fish-keepers from the bad ones. I had to re-home lots of fish so far from listening to my LFS. They really have no idea it seems like(most of the time).
Yesterday I overheard a young man and his girlfriend buying a 20g tank, I heard oscar tossed around.. when the employee left to get him something, I asked him what he was planning on (in a nice way). He says "oh I'm getting that black Tiger Oscar up there, he's really neat"
I explained that the tiger oscars grow really big, and require a MINIMUM of 55g tank(that's even pushing it), showed him on my hands how big they get.
He goes " ****... why is this guy telling me it's ok?"
I said because they need sales.
He made the decision to get the tank, but leave the oscar. He said he was gonna go read online.
I felt like I saved that oscar, and that guy a lot of frustration.
ANYWAYS... You're gonna either have to invest a lot of money for those two Jag's, or just take them back and get something peaceful. You can really do some neat stuff in 30g.