I tried again with neon tetras. This time I bought 20 of them when PetsMart had them on sale. I put them in a 20 gallon aquarium with the water temperature at 78 degrees for a week to make sure they were nicely acclimated and weren’t going to die from something else. Then I slowly raised the temperature to 83 degrees over the course of about a week. Then I introduced them to the big aquarium. This time I didn’t have any die off. A few weeks later, PetsMart had them on sale again, so I bought 30 more and did them same thing.