Unexpected Loss

Hi all, I had an unexpected loss in my new tank . A male swordtail,that i had brought over from my old tank . (I had actually bred this fish from older stock and he was my only survivor) Anyway ,one morning he was floating . I have been cgecking water parameters daily as with it being a new tank set up I was expecting some problems to crop up, but all my levels were fine, 0,,0,0,ppm Nitrite ,ammonia and Nitrate across the board and a PH of 7.0. My only recent actions were to dose with Flourish excel to help plants and slight algae. I underdosed anyway . Would Excel have caused this sudden loss. No other fish seem affected . Any idea's  . Col . PS great website .

Hi Col. Welcome aboard! 

Fish definitely dislike products like Flourish Excel in high doses, but as you under-dosed it seems unlikely that was the cause, especially as the other fish seem unaffected.

The usual symptoms of overdosing would be seeing the fish gasping at the surface.

Sometimes it's just one of those things and you can't really tell what caused a sudden death.

You said you'd moved the fish over from another tank, how recent was this? How old was the fish?

How old was the poor lad? You say he was the only survivor of a family that you bred?