Water Temperature Question

[GoofyGarra]

During the day fish move around and have faster metabolisms and use more oxygen, so their higher metabolisms use more heat.

At night the fish dont move around all that much so their metabolisms are slower.

So do fish need a heater at night? Or would they tolerate say mid 60s at night going back to the 70s at day?

Working on a power limited tank and id want to use a window as a heat source, hence this question. (green water is a desired affect on this tank).

[beastie]

I think it really depends on the fish,no?

I have three unheated tanks, all sit around 21C during the day, since I heat the house, they dont drop much during the night. They are low flow though so the mixing of water temps is a question. Some fish will tolerate 60F, some wont

Edited October 18, 2023 by beastie

[GoofyGarra]

On 10/18/2023 at 5:52 AM, beastie said:

I think it really depends on the fish,no?

thats a fair question. Probably platies or some other kind of cool water fish like white clouds. Id also love to try something super cool like Gold Barbs, which i think can tolerate cooler waters as well. If i could find them rice fish might be cool as well.

Edited October 18, 2023 by GoofyGarra

[beastie]

Most of these along with like indestructible endlers can survive these swings.

I think some fish are more tolerant than others, I keep clown killifish, which some sources say to keep 22C and above in a 20-21C, same for indostomus though they are ok with 18-22. My Minnows do fine in the unheated tank but for breeding they also do fine in a 25 degrees, no issues

 

For you best would be to have something write the temp during the night for few nights, to see if the window doesnt lower it too much, you can expect it will go to 60F, but what if it goes lower? Some heaters have a sensor for temp, though those are costly. And as I said, for me, low flow tanks, even with heaters, have very badly distributed water temp, as it sometimes just sit in one place, some places are colder....depends I guess 🙂

[GoofyGarra]

On 10/18/2023 at 6:15 AM, beastie said:

Most of these along with like indestructible endlers can survive these swings.

endlers could be fun, the plan is to heavily plant the tank with Val and Guppy Grass so a colony of Endlers could do great. Im also hoping to maybe add in some cherry shrimp  later in the tank's life, so endlers would work great with those too.

On 10/18/2023 at 6:15 AM, beastie said:

For you best would be to have something write the temp during the night for few nights, to see if the window doesnt lower it too much, you can expect it will go to 60F, but what if it goes lower? Some heaters have a sensor for temp, though those are costly. And as I said, for me, low flow tanks, even with heaters, have very badly distributed water temp, as it sometimes just sit in one place, some places are colder....depends I guess 🙂

I need to figure out the ambient room temperature at night. If its stays above 65 i should be fine, otherwise i might have to use a heater.

Edited October 18, 2023 by GoofyGarra

[Biotope Biologist]

Don’t measure ambient measure water temps. Water is a thermal insulator. It does not swing temperature as much as air does.

 

I would say most fish are fine with temperature swings of 5 degrees between night and day. I don’t use a heater and I like my house cooler. 
 

Air temperature measures at 65-68

Water temperature measures at 68-70 sometimes 72 if the sun is strong enough. My fish prefer colder water. But there is not a huge difference between night and day temps.