Fish dying of cold water?

[robertmarda]

Over the weekend the heater in our 20 gallon tank at work failed. I found our upside down catfish and 2 gold pristella tetras dead. Later in the day our mother platy died. This morning I found our other 2 gold pristella's dead and one of our glow light tetras.

In this same tank I still have 1 adult molly, 1 juvenile molly, 1 adult platy, 1 glow light tetra, and 1 baby platy (born over the weekend).

My question is: Are small tetras more susceptible to cold water than mollies and platy's?

The temperature was 68F when I arrived Monday morning. The temp in the tank is now 75F.

 

[Menagerie]

My question is: Are small tetras more susceptible to cold water than mollies and platy's?

Smaller fish may have more problems dealing with the cold. Aside from that, do you know how quickly the temp dropped? That is a major stressor and could be responsible for the deaths.

 

[robertmarda]

Unfortunately no. When I left work friday everything was fine. I didn't check the temperature that day and hadn't for a while. Then when I came in on Monday I noticed the dead fish and noticed the temperature was low. I suspect it was colder over the weekend.

 

[rubysoho]

hmm, that is interesting. I had heating problems while I was away this past weekend, and one of my tanks dropped under 60 degrees! However, all three female bettas and 2 african dwarf frogs were alright. I slowly worked the temp back up (and right now it is at 74 degrees). Have you checked your water perameters? Is your work place heated over the weekends? My apartment wasn't so maybe if your's cut the heat friday night, it could have dropped very quickly whereas mine (I'm guessing) was a slow drop.

 

[robertmarda]

I suspect the heating was shut off Friday and the temp drop was quick. I only have a test kit of pH and Ammonia here at work.

 

[Menagerie]

A 20 gal tank would be prone to a sudden loss of heat. They have a large surface to volume ratio.

 

[robertmarda]

I brought my test kit from home to work and checked the water parameters this morning and found the following:

pH 7.6
Ammonia 0.25 ppm
Nitrite 0.5 ppm

So it appears a combination of the cold water and toxins caused the problems.

I did a 20% water change and the nitrite level dropped to .2 ppm.

I lost 3 more fish. Now there are only 2 in this tank.

 

[Menagerie]

The water parameters are definitely a cause for the loss of fish--more so than the drop in temp. What kind of filter are you using? You might want to bring in bacterial squeezings from a tank at home to help out the bacteria in the office filter.

 

[robertmarda]

I have an established 40 gallon tank about 10 feet from the 20 gallon tank. What do you mean by squeezings? Or is there something better I can take from the other tank?

The filters in the two are not the same size of course, but I could easily move the activated carbon (assuming bacteria columns are there) and set that in the tank itself for a few days (if that won't hurt anything).