Depending on where you live, can you post an add somewhere to try to rehome some of the fish? Really the most responsible thing to do would be to try and rehome the tiger barbs, or rehome your golden and rosy barbs and the molly. Or, alternatively, get another tank for the tiger barbs or the other fish so you can separate them.
If you really cannot rehome or return any of them, you could potentially try this (for total number of fish):
6 rosy barbs
6 golden barbs
8 tiger barbs
and your 1 molly...
This would be a heavily stocked tank though, IMO, and would require a suitable filter and large weekly water changes. Adding plants would help with water quality. I would aim to change 60% of the water weekly if you were to add that many fish. It is far from ideal and your tiger barbs could still cause a problem.
If you really cannot rehome or return any of them, you could potentially try this (for total number of fish):
6 rosy barbs
6 golden barbs
8 tiger barbs
and your 1 molly...
This would be a heavily stocked tank though, IMO, and would require a suitable filter and large weekly water changes. Adding plants would help with water quality. I would aim to change 60% of the water weekly if you were to add that many fish. It is far from ideal and your tiger barbs could still cause a problem.
