Welcome
J
jdaniella
!
The fish in question is indeed a tetra, and indeed it seems to have dropsy. I would not expect it to live much longer. It is likely that water quality/maintenance routines in that tank have not been the best. That is something that is good to improve on, and good routines set in place BEFORE getting any new fish. There is not enough info for ascertaining what happened with the catfish (or the tetra) so it is better to make that a different story.
A good way to getting good advice here, is to provide relevant information in a systematic manner:
1- aquarium size
2- fish currently in (including any snails, frogs, turtle, anything)
3- filtration
4- Any living plants?
5- What kind of substratum (none, sand, gravel, what types?)
6- Frequency AND volume of water changes. There will be a range of preferences (depending on a number of things), but some water should be change at least once per week. I change 50-80% per week.
7- If you have a test kit, info on the water available to you water would be useful (pH, hardness,GH, KH). If you don't have a test kit, some information can be ascertaining from your city's water report.
8- How often do you guys feed, and what do you feed?
With this info, good folks here can help you develop routines that will result in healthy fish and lots of enjoyment. Without it, it is difficult to offer meaningful help.
One thing NOT TO DO at this time would be to go get more fish.
I hope this is clear and useful, and that you see why it is important. Then the real improvement can occur.
Good luck!
There are several things to keep in mind when