I would not use a 2.5gal tank for quarantine purposes - I use a 5gal for that purpose and I feel limited - not only in how many fish I can put in there comfortably but how much room the new fish have to move around - new fish need space to hide when they 1st arrive (I put a fake flower in mine and keep it bare bottomed) as well as to explore when they finally feel more comfortable.
From what I've learned here, a 2.5gal is good only for small shrimp & snails.
46 gal fw tank with black skirt tetras, neon tetras, spotted corys, cherry barbs, otoclinus, snails & 4 amano shrimp - plastic & live plants
5 gal QT
Remember: Our job is to take care of the water our fish live in