What happens to fish when they are cold?

burgesi

How do sudden temperature changes affect fish and what about fish that are in cooler or warmer temperatures than they are used to?

For example, in winter, if the tank heater dies it can sometimes go unnoticed by the owner and tropical fish are left in water about 14 to 17 degrees celcious. The fish don't die, but how does it affect them long term or short term?

ladayen

Well short term... I'll give you this personal experience.

I ordered a bunch of fish a few weeks back. 2 heatpacks were placed in the box, taped to the top. There were 2 layers of bags. The top layer of bags and the fish inside were fine when they arrived. The bottom layer.. not so much. The temperatures had dropped overnight to a balmy 14 degrees farenheit. The fish on the bottom all appeared dead. Most were belly up, the Bristlenose Pleco wouldn't move even when poked through the bag. We noticed a bit of movement in a couple of bags so we decided to stick them all into our tanks(fish in bags still) and see what would happen when they warmed up. Eventually nearly everything came around and 3 weeks later is doing fine. One of 10 Otos was dead in the bag. 2 female congo tetras died within 24 hours 1 other female congo took nearly a week before appearing normal. Bristlenose Pleco, 2 dickfeldi, 6 congos total, 10 otos and some plants composed the bottom layer.

I read another forum post once about a guy who got mad at his cichlid(cant remember exact species) because it had killed another far more expensive cichlid. He proceded to fill a bucket with tap water as cold as he could and put the fish in it for about 5 minutes. The fish survived but from that point on became very passive and docile, likely a sign of nerve/neurological damage.

fish monger

I had two 8-9 inch Oscars in a 55 gallon tank and the heater failed one cold night. I found them motionless on their sides at the bottom of the tank. They started to recover as soon as the temperature increased and seemed completely normal within hours. They both died about 6-8 months later. Not sure if there was a connection.

Adamson

Is that the same guy who kicks his dog and loves cock fighting? Though it is kind of funny in a sick way, it is really sad..

Termato

That's horrifying. wow. Why don't you do some research before putting all those fish together!?!

Poor fish!

Tazman

Just a point to consider, if you ever have a fish which is cold due to a heater malfunction...

Raise the temperature back up EXTREMELY SLOWLY, 1-2 degrees every hour..raising it from cold to hot with a new heater can sometimes shock it to death. Most fish will tolerate cold temperatures for a short period of time, they slow their metabolism down...like a human would if alive and extremely cold.

Treatment for hypothermia in humans involves raising the body temperature up slowly, quick change can lead to a heart attack and death quickly...same applies to fish. Raising it back up slowly also helps reduce the stress it is encountering from being cold.

Adamson

One time I had an eel literally jump out of the back of my aquarium, out the window, it fell three stories before landing in a pile of snow. Thank god a neighbor saw something fly out my window, she came over and asked me what happened. We went down and outside to see the eel flopping around in about 6 inches of fresh powder. Still have no idea how he made the landing, and then managed to stay alive in the snow. After all it must have fell almost 30 feet..

Termato

WOW!!! Were you able to save it after that!?

Adamson

Yeah it ended up perfectly fine!
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