Inherited A Tank. Killing The Fish!

[gowing238]

I have recently moved home and was left a tropical fish tank by the previous owners. I recently added 8 x ray tetras and 8 black diamond tetras. also 2 live plants. i got up one morning and they were all at the surface gasping for air. i removed the plants and pumped in air and managed to save most of them. but every morning i get up and have one dead or dying fish. they swim around frantically and slightly on their side and suddenly die. all the old fish that came with the tank r ok. Anyone got any ideas on whats wrong?

 

[The-Wolf]

sounds like you are experiencing a pH crash during the night.
test your kh level, I'm betting it is very low or non existent.

Also test the waters pH at least an hour before lights on and compare that to
the same test at least an hour after lights on. if there is a difference that is the cause.

click the water link in my sig for ways to deal with low kh and an explaination of the other things
that is in your water.

if you don't have a test kit get a lfs to do it but remember the pH sample from the dark test needs to be kept
dark as the light will alter the results.

 

[bubblesburst80]

hope you sort out your problem

xXx

 

[KhaosInc]

how big is this tank, and what was in it before.