Aggresive tank mates plus goldfish

Ecuij

New Fish
Feb 2, 2017
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#1
Hi! I'm posting in a bunch of forums because I really need help...​
At my job we have a fish tank and its not doing well. They have had it for years, far before I started, and the staff who used to take care of it left. Since then it was periodically taken care of by someone else, but the tank isn't doing well. I have begun taking care of it as I couldn't stand to see the fish die. From what I understand the store who selected the fish did not choose fish that go well together.
In a 55 gal there was a (forgive me if any of this is wrong I think fish are pretty but am just learning about them) kissing fish, an Oscar, a Jack Dempsey, Pleco and a Tetra that looks like it could be a Buenos Aires or could be a Barb? (No one knows what kind of fish there are, this is from asking friends and staring at fish pictures. By the time I started only JD, the Pleco, and the Tetra(?) were left. I took over when the Pleco was struggling to live. Sadly he passed on. Since then I have scrubbed the tank and we have them feeder fish (Goldfish, as recommended by the store) and two of the goldfish turned into pets for the others in the tank.
The big fish are still not doing well and are losing their colors. Which is why I am having a hard time figuring out if the Tetra/Barb is what I think it is.
Anyway. My bosses requested to get a school of fish to make the tank more lively. I know they can't go into the same tank as JD and the Tetra/Barb so my bosses bought a 29 gal. Upon further reading and research I have learned that Jack cannot go into such a small tank.
My questions for you guys is what kind of fish can we put in with them, and any advice for making them happier? I'm trying to find a good balance between what my bosses want and what is best for the fish. I can include picture of the fish and the two tanks if you guys need them.