So, I wasn't having any luck finding info on this online anywhere, and I was curious what some of you all thought.

For all the reptiles I have here, they all have a day/night temperature range. They get a basking light "daytime" (or are outside in the summer) for a good 12 to 16 hours a day, and then the heat lamps goes off to make it essentially night time.

For the fish, the lights are set on timers so they get 8 to 10 hours of light a day, however the heaters are all on 24/7. Why is it that no one seems to have the heaters turn off at night as well? In the wild the water would cool off in the evening and then get warm again when the sun comes up.

With all the talk of doing cool water changes to help start breeding, wouldn't something like that have a similar benefit?

I thought I would see some type of reply to this post. The only thing that I could think of was that water retains it's temperature at nite. Water temps would only change more in different seasons and to mimic that people do cool water changes to help start breeding. I'm just guessing since I to could not find much on the subject.

I would agree with CW. Since water retains it's heat much better than air I would guess the temps would only change 1 or 2 deg. at the most. Water temps change dramatically after heavy rains which is similar to doing a cool water change.

saint_felony wrote:

So, I wasn't having any luck finding info on this online anywhere, and I was curious what some of you all thought.

For all the reptiles I have here, they all have a day/night temperature range. They get a basking light "daytime" (or are outside in the summer) for a good 12 to 16 hours a day, and then the heat lamps goes off to make it essentially night time.

For the fish, the lights are set on timers so they get 8 to 10 hours of light a day, however the heaters are all on 24/7. Why is it that no one seems to have the heaters turn off at night as well? In the wild the water would cool off in the evening and then get warm again when the sun comes up.

With all the talk of doing cool water changes to help start breeding, wouldn't something like that have a similar benefit?

Wow. Somehow I missed this post, otherwise I'd have given you an answer a lot sooner.

I thought of this years ago when my Limnology prof started discussing thermal gradients and thermoclines in bodies of water, including seasonal and daily ambient temperature variations and their effect on these phenomena. Even in tropical regions, bodies of water do exhibit temperature drops of a few degrees at night as well as a temperature gradient by water depth beginning with warmer water at the top and cooler waters at the bottom. In The Cichlids and all the Other Fishes of Lake Malawi, Ad Konings mentions the average temp of the lake and the temperature gradient by depth, and how it allows fish to stay at a comfortable temperature by adjusting their height in the water column. The same has been shown across the globe with fish from tropical through cold temperate regions.

I experimented with this in my tanks in college. Turning the heater off isn't the answer, because an aquarium has too small of a volume of water. Whereas a lake has millions of gallons of water to act as a heat sink and prevent the temperature from dropping more than a degree or two or three, an aquarium has a small volume of water. In an aquarium, each gallon of circulating water contacts the surface area dozens of times, radiating heat to the atmosphere. In a lake, each gallon may touch the surface once, if at all. Actually this can be broken down into as small a unit of volume as you like. Regardless, whereas the lake may only lose a few degrees at the surface, an aquarium can lose 10 degrees or more across the entire volume. The only way to do this in an aquarium is to turn each tank heater down a couple of degrees each night, and that would be a PITA. I don't know if there are heaters out there that can be set up to raise and lower on a 24 hour cycle automatically; there may be but I'm sure they are as expensive as hell.

Large tropical rivers exhibit many thermal similarities to lakes, so the fish have the same options. Incidentally, I got to wondering about the Amazon a while back after reading 'bout piraiba and red tail cats being most common in deep holes within the river. I found a reference to the water at a depth of 130 ft (roughly 40 m) being in the high 60s to low 70s. Red tailed cats and tiger shovelnoses are often caught as deep as that. Anyways, shallow tropical rivers and creeks stay at a warmer temperature than a lake and lose heat, but the warm ambient air temperature and high humidity keeps the heat loss to a minimum considering the volume. IIRC, the high amount of organic material in these stream beds helps to maintain the heat as well, kinda like a compost pile creates heat, but I forget the exact mechanism.

As I mentioned before, fish can move up and down the water column to stay in a comfortable temperature zone. They do this on a constant basis in the wild, over the course of the day, and so a daily temperature increase or decrease really has a very minor impact on their biology. All in all, water is a much more stable environment from a temperature standpoint than air.

WYite

Now that WYite has mentioned the temp differance at lower depths, it made me remember that I have experianced that when swimming in the lake where we have our trailer. You can feel the temp change in water as deep as 6 feet when you dive to the bottom.













For all you people like me have no clue what Limnology is Wikipedia-Limnology

I was thinking about how it could be done and a very easy way would be to have 2 heaters set up in the tank set at 2 to 3 deg temp difference. Put them on timers so the warmer one is on during the day and the cooler one is on at night. Just a thought.

I would thing though that like Wyite mentioned the fish probably move to a warmer part of the lake at night to maintain a similar temperature. just speculation though.

I can tell you this If your going to breed goldfish need have to have a seasonal cool period and a shorten photo period to trigger spawning

Also in some weather conditions it is not unusual to see 5 to 10 degrees drop in temperature between sunset and sunrise in the grow-out houses but the drop is generally some where between 70 and 80. My cold water fish can easily handle a 10 to 15 degree drop if done over 8 hrs


Rick

dirtydawg10 wrote:

I was thinking about how it could be done and a very easy way would be to have 2 heaters set up in the tank set at 2 to 3 deg temp difference. Put them on timers so the warmer one is on during the day and the cooler one is on at night. Just a thought.

LOL, that would be an easy way. But, no, not me...I always miss simple solutions like that, duh. I never think of things in the scale of one or two tanks with my extreme tankage. That would take a LOT of extra outlets in my case...

WYite

Wyomingite wrote:

dirtydawg10 wrote:

I was thinking about how it could be done and a very easy way would be to have 2 heaters set up in the tank set at 2 to 3 deg temp difference. Put them on timers so the warmer one is on during the day and the cooler one is on at night. Just a thought.

LOL, that would be an easy way. But, no, not me...I always miss simple solutions like that, duh. I never think of things in the scale of one or two tanks with my extreme tankage. That would take a LOT of extra outlets in my case...

WYite

It would definitely be a lot tougher with the amount of tanks you have Wyite. You'd have to have a centralized sump and filter for several tanks in order to pull off something like that with a ginormous amount of tanks.

cooltow1 wrote:

I can tell you this If your going to breed goldfish need have to have a seasonal cool period and a shorten photo period to trigger spawning

Also in some weather conditions it is not unusual to see 5 to 10 degrees drop in temperature between sunset and sunrise in the grow-out houses but the drop is generally some where between 70 and 80. My cold water fish can easily handle a 10 to 15 degree drop if done over 8 hrs


Rick

Good info Rick. I need to start keeping some cool water fish.