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Discussion Starter · #1 ·
I'm in day 7 on my cycle for my 10 gallon reef tank and I notice that my tank has been at 80-82 during the day and at night it stays at 80. I've turned down the heater and it's still hot. Where I live we get very hot summers and after summer is over it's pretty much cold after that what should I do. It's not a big deal now since I don't have anything I'm the tank that could die but I'm just planning ahead of time. Since later I will add fish and coral also I have no light on it at the time.
 

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What is your room temperature? If you have no lights on in the tank and no heater shouldn't the water eventually reach room temperature?
 

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Discussion Starter · #6 ·
Well the temp during the summer is from 78-90 and I have 7 windows in my room so it gets really hot in my room even with all the windows open! I lowers my heater today and it's been a strong 79 I'm going to see if it stays like that during the day.
 

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for what its worth, Ive ran reefs at 80-82 with no ill effect... in fact the growth and health of the tank was probably better than previous tanks ran w/ a chiller
 

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I dont think you need to worry about it... a temp that doesnt fluctuate is more important than keeping the tank at exactly 77, in my opinion
 

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yup
 

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found this

The rate of cooling of the water depends on many things. The first is the thermal gradient, which is the difference in temperature between the water and the surroundings. In this case, the thermal gradient is between 100 degrees and 25 degrees.

As the water cools, the thermal gradient gets less and less, causing the cooling rate to slow. Heat will move quickly from 100 to 25, but when the water gets to 50, the 50 to 25 thermal gradient makes the cooling slower. Once it gets 25.5 and only has to get 25, cooling is very slow. The last little bit, may take longer than the lion's share.

The next consideration is the rate of heat transfer. If we have the water in an insulated cooler or within a thin walled copper pot, the heat transfer rate is faster in the copper pot, because metal will conduct the heat better. The insulated cooler is designed not to conduct so the heat transfer rate is much slow for the same thermal gradients.

Say we pick the copper pot, since this is faster; has a higher thermal conductivity. The heat transfer has to go from the water, into and through the walls of the metal pot, and then to the air. This heat transfer will influenced by the convection currents that are set up on opposite sides of the metal container.

The water touching the inside wall of the container will cool first. Since cooler water is heavier than warmer water, as this interface water cools, it will sink. The air on the outside does the opposite, since it is being heated at the wall. The warmer air will rise. These two flows are called free convection. This dynamic movement is the main source of heat transfer.

Th convection of the cooler water, downward, requires new water move in to occupy that space. This is warmer water and restores the thermal gradient. The rising warmed air requires new air move in. The new cooler air comes in and takes its place also restoring a higher gradient. The dual speed of this convection will determine how fast it can cool.

If this convection is done passively it is called free convection. If I wish to speed up the heat transfer, I can use forced convection to get the water and air convection moving faster. I might set up a fan on the outside to move the air faster. Or I might add an agitator to the water, so the water mixes quicker. Forced convection transfer the heat much faster.

You also need the heat capacity of the water. The heat capacity reflects the amount of thermal energy a material can hold per unit of mass. Water is unique because its heat capacity is huge for its size. All else being equal, since water has one of the highest heat capacities, water will take longer to cool than say the same mass of alcohol.

http://lofi.forum.physorg.com/Question-About-Temperature-Change-In-Water_44484.html

for some reason both my tanks are always the same temp even though I only have one heater. we keep our a/c at 78 and the tanks are 80/81 at night and only 82 in the day. I live in a trailer and it gets hot in here! the nighttime room temp usually gets to 80 fairly quickly after the sun sets (8pm?) and will stay here until about 8am.
but during the day our a/c has problems and is usually 87-92 on bad days (probably 2-3 days a week right now) and 84-87 on decent days but it doesn't seem to affect the tanks much. I have only seen the tanks at 84 once but constantly stay at 82 when the sun is up.

my evap is also about a gallon a day with the 55gal DT having no cover and about 95% of my 55gal sump covered. I also have an air stone (hooked to two average walmart pumps)which is probably causing more evap then need be. a quick searched just told me an air stone causes more agitation causing more evap and helping to cool the water a degree or two. you could try adding an airstone to your sump like I did. I have it in my bubble trap, it makes quite a bit of foam and helps to keep some larger, lighter detritus (such as strands of green algae) trapped on the glass. I probably collect enough to fill a tablespoon every few days so if its removing something im happy to just wipe the surface to clean it :)
 
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