I have a pair of Oscars in a 90 gallon tank. They are 4 years old. I keep them in my below ground family room. I'm in the middle of a boiler repair so my house has been cold. The below ground family room much more so then the upstairs. Up until the boiler went out the below ground family room was usually about 21 degres C. Lately it's been colder. More like 16 degress C. There isn't a heater in the tank. There haven't been any signs of stress or any other weird behavior until today. Another ciclid in the very same room, in another tank, is fine. The Ocars broke their heater so I'm guessing the tank is about air temp.

I came home from work a couple hours ago and one of them was lying on the bottom. He didn't look dead but he wasn't moving. I moved him to a little warmer water and still no reaction. Is there a possiblity that he will recover?

Do fish like this go dormant if it's too cold? Do they hibernate by not moving? How cold is too cold for them to survive?

Thanks!

Fish will probably not do much if they get too cold, so yes, they would probably be motionless just lying around. Since I've never frozen one of my Oscars to death, I couldn't tell you at what temperature an Oscar will die. However, I shouldn't let the temperature get below 20°C for too long. 16°C is a little bit too low and I think the fish would be stressed if the conditions were like this for any period of time.

Even though fish don't show signs of stress, they still can be stressed. When fish get stressed, it can increase the chances of them developing disease such as White spot, or even worse, hole in the head disease. Unfortunately, there's not much you can do if you've got a problem with heat. This is why I like to keep my water temperature at around 28°C. If the power does go off, you've got a little bit of time before the temperature drops too low

I would advise you to get a heater in your tank, 21°C is the absolute minimum I would like my temperature to stay at. Even then, you might have other fish that can't tolerate a temperature that low.

just because the room is 20 C doesnt mean ur water is. water is usually colder then the air. def get a heater and ur os should come right back to life.

Thanks for your help. I did put another heater in the tank just prior to my post so the other fish wouldn't end up the same way. I guess if they break that one as well I'll have to go to a sump style filter and heat the tank externally.

I thought he was showing signs of life last night but today it's aparent that I've lost him. I was unable to detect any signs of stress induced disease as you mentioned. I feel terrible--it's funny how attached we can get to these guys. I've had the pair since they were the size of a silver dollar.

I'll wait a couple of weeks to make sure that the remaining oscar is doing well (there's a 16" pleco in the tank too) and then think about finding a tank mate.

Again thanks.

sorry to hear about your loss and yes you can get really attached to your pets. in case you didn't know they sell shatter proof heater for active fish here in canada. im not sure where your from but it could be something to look into

Shatter proof heater-great idea! I'll look into replacing the one that I just put in, if I can't find one locally I should be able to get one on-line.

Thanks again

or you can get a heater guard, it a plastic cover. Your oscars can still throw it around if they want but the cover protects the heater