can anyone tell me what i did wrong

[Eric1972]

my first aquarium i got 5 months ago i read and do everything by the book. my tank is a 100 gal i do water changes once a week keep all my levels perfect i have 1-florida gar 1-longnose gar 1- 10-inch frontosa i did my normal water change tonight and just as my tank finished filling my frontosa started acting crazy all my other fish are acting fine. within 20 min he died. i wanted to be sure so i checked and dbl checked my water temp is at 79..my ph is at 7.6..my amonia is 0ppm..my nitrite is 0ppm..my nitrate is at 0ppm..what did i do wrong.. ive done this same water change every week i even have a temp gun and put exact same temp in as the tank is... would really appreceate any input

 

[CanadianKeeper]

Could have just freaked out and bumped its head hard. Happend with my buddies ID shark.

 

[clgkag]

Did you use dechlorinator when you did your water change?

 

[Eric1972]

yes i used prime always do

 

[Eric1972]

i know im new and jumped into bigger fish but thought i had it right

 

[Dahawkster15]

i know im new and jumped into bigger fish but thought i had it right

Are you testing your water with strips or with drips?

 

[Eric1972]

i bought a freshwater master kit and use it..its drips

 

[Dahawkster15]

i bought a freshwater master kit and use it..its drips

Hmm...I don't know. Are your other fish still fine? One of the experts will give you an answer eventually

 

[Eric1972]

my other fish are doing fine. i have a bgjd she is breathing hard but she always has i think shes really old.

 

[imusuallyuseless]

Amount of chlorine in municipal water supply can vary. Dose of prime may be adequate MOST of the time and sometimes inadequate. Killed of almost an entire tank once figuring wc was solution, in truth was the problem.