Hi Guys

[Pistol]

Hi every one , I am new to the forum . I have been keeping Fish both salt and fresh Water for 20 years now. I live in Ontario Canada and have a 75 gallon fresh water tropical tank. I have small dwarf chiclids and tetras in my tank.My tank is 3 months running .In my tank there were 55 fish ,My filter is a Ehiem Canaster filter along with a hagen C4 filter. My temperature is at 79 degrees. I do 1/3 water changes every two weeks. My water quality is excellent at all levels.

This is the situation....my heater malfunctioned about a week ago and the temperature in my tank dropped to 72 degrees. Unfortunately it was late at night and I did not have a replacement heater. I therefore had to remove some water and then add warm water until I was able to bring the temp up to 79 degrees. Through the night the temp had again dropped to 72 degrees. It took me about 8 hours to have a new heater installed. The temp may have dropped even further by that point. The next day I noticed a couple of fish had spots (ick). The following day I purchased the medication (ickX) and added it to the tank. It has been 4 days of treatment and I have lost a total of 32 fish. The first day I lost 15 and they have slowly been dying off each day. I don't see any more ick on the fish at this time and still I lost 4 today.

Any thoughts of what might be going on?

 

[fm1978]

My initial thoughts would be stress/shock, one way or the other. I assume you know what you're doing after keeping fish for 20 years so all I can think of, since your water seems fine (apart from the temp) is that large temp fluctuations have exacerbated a problem that may have been there to begin with but not presented very quickly. 
 
The ich was probably already working on your fish, given that it started to show the very next day, but with the temp bombing and then rising again it's perhaps shocked their bodies affecting their natural immune responses (which might normally have been able to cope) and allowed the ich to take over very quickly.
 
It's either the temp drops and rises or ich or a combination of both. I'd most certainly continue the treatment/prevention for ich for a while even after symptoms have disappeared, and obviously keep an eye on those heaters before thinking about restocking.  

 

[WILDER]

When temp drops fast and then trying to fetch temp up again fast can cause stress, You can sometimes expect outbreaks of ich, swim bladder, columnaris. All due to unstable temps in a tank.
 
Sorry for your loss. R.I..P.
Have you noticed any other symptoms a part from whitespot?
Fish not being able to maintain balance in the tank.
White fluffy cotton wool on fish body, or fins?

 

[Pistol]

thanks for your thoughts