50 Gallon Tank Does This Happen Often?

I went to Petsmart Friday and got got a few dalmatian molly and some Black molly. The next day one of the dalmatians was dead so I took it back up to the store with some water since they do free water test. When I got there and was waiting for someone I notice they had 2 dead Dalmatian in the same take mine can from (and the Black). They test with strips and can to the same results (everything in the good). I swapped the one out. Next day I had two dead however, no of the Black has died.

Is this them just getting some problem fish? How often does this happen from a store such as this?

 

They were probably sick at petsmart. Many chain stores don’t take care of their fish properly. Did you cycle your tank?

 

Are you quarantining the new fish?

 

Yes I have a smaller tank

 

Yes I have a smaller tank

One possibility is the pet shop uses salt and you did not. Mollies are very sensitive to this. If they do use salt you can acclimate them to saltless over time through small water changes.