fish death

Question
Yesterday, I noticed my female swordtail laying low in the tank; this morning she was dead.  No signs of disease from her or any other fish.  She was new to the tank as were several others. Last water change was yesterday morning.  Is there something I should do, or treat the water with following the death of a fish to prevent any outbreak of disease I did not see?

Answer
Hi Debbey,
If there is anyway you could test your water to check the ammonia, nitrite, and nitrate levels that would really help. We need to know if your tank is established and cycled, which of course is indicated by ZERO readings for ammonia and nitrites and nitrate readings of varying levels. It should ideally be around 20.

If you have ammonia or nitrite readings that's a sure cause of the fish loss. It's always better to be able to test your water at home. But you can bring a water sample to your petstore.

As a precaution and if in doubt, a 30% water change for the next few days is the best step to take. Until you can be sure your water's test results are where they should be. You can eliminate that huge factor and consider other possible causes to the swordtails death. Sometimes fish are just weak and stressed and you can get bad batches from petstores sometimes. I hope you have better luck in the future.

Best wishes!
I hope this helps,
Karen~