Is a goldfish tank warmer at night than in the morning?

Question

I have a 10 gallon tank with two goldfish. Being they're coldwater fish, I do not have a heater in the tank. I turn the tank light on during the day when I wake up and off at night when I go to sleep. I do not have a thermometer in/on the side of the tank (go ahead and flame me I know you want to.)

Recently, much to my surprise, I noticed a lot of very tiny, see-through baby fish, that were undoubtedly freshly hatched goldfish. I know that it takes a lot of certain conditions to encourage the fish to breed and I wasn't even trying. I know that goldfish need very warm water to get "in the mood."

The fish like to nibble at my fingers so occasionally I put my fingertips in the fishtank. Usually it's very warm, but I work in the daytime so I've only done this in the evenings. But today I have a shift in the evening, and I dipped my fingers in the fishtank at about 11:30am, and the water was cold (or as cold as goldfish water gets).

So I'm wondering, since the light is off at night and on all day, is an average goldfish tank warmer at night before you turn the light off, than during the day when it's only been on for a few hours?

Just to add: The fish are not directly in the light of any windows. The tank is against a wall about two feet from a parallel window, it's usually in the shade.

The window in my room is on the north side of the building.

I live in Minnesota, winter is dawning and we've had a few snowfalls.

The room generally stays between 70 and 78 degrees or so, depending on whether I get hot enough to open the window. My apartment complex offers free heating so it's never too cold in here.

Answer 1

So long as the room temp stays a constant the water will be at its warmest just before you turn off the light. Another condition that might play in this is if the window is on the west side of the house which would allow the sun to heat up the room in the evening. Or if the window is in the East it will bring up the room temp in the morning.

Hope this helps
PK

Answer 2

Congrats on the fry!

I doubt that any changes over the course of the day are responsible for the spawning - usually it's the overall (average) temperature. Depending on where you live, you may be experiencing either a spring or fall, and this brings a temperature change - especially if you live far enough from the equator that you need a heater to keep where you live warm enough to be comfortable. For example, where I'm at, it's gone from summer to a reasonably warm fall, although the temperature has cooled over summer temperatures. Just recently, it's become cool enough that the heat has to be turned on during the day. To a fish, this means warm, cool down, warmer again. That is usually the type of temperature change that brings on spawning. The opposite happens in the southern hemisphere, where heat may have been on, then it's gotten warm enough outside that the heat wasn't always necessary, but now it's getting warmer outside as summer begins.

ADDITION: The lights would make the water warmer if you're using incandescent lighting (screw in bases), Fluorescent lighting doesn't produce as much excess heat, so this wouldn't change your temperature as much. It would also make a difference if the tank has a full cover, or just the part directly under the light, since a full cover would trap heat. So after being on all day, the tank could be warmer from the lighting.

Answer 3

Hi Megan, That's quite rare to actually have fry & they sound like they trust you already. To answer your question-yes it probably is slightly warmer in the evening than the morning because the heat from the light on all day probably will heat such a small volume of water as 10 gallons up.

You might want to consider upgrading your tank now for your 2 fish-they would ideally like to be in a 29 gallon. Then the fry could have the 10 gallon as a nursery without the danger of being eaten by Mum & Dad!!!

Answer 4

if you're asking whether your tank gets warmer by the end of the evening than when it has been sitting with the light off all night i think its pretty obvious. the light will heat the tank. when theres no light on it i guess it would be relatively colder

Answer 5

Goldfish are very hearty, but if their is a large fluxuation in temperature they can go into shock, most people use heaters really to stop the fluxuations from being so great. but if they are breeding I think you are OK

Answer 6

It really just depends on the sunlight, and the heat in the room.
If its all the same then it will stay the same