Pet Forum / Aquaria / General / August 2006

If your thermostatically controlled heater is holding the temperature
you want in the cold months, there is no need to change the thermostat
in the warm months.

In warm months, as you already know, the problem is keeping the tank
temperature cool (hold same temp as in winter).

I live in a hot west Texas town, most hot days run over 80F and the
house can easily absorb enough heat to go beyond (think of car in sun
with windows closed).

I have my house air conditioned and the thermostat set to 78F in the
hot climate, whereas in the cold I set the thermostat to 74F and rely
on the tank heaters to raise from ambient 74F to tank temp of 78F/

So, do you have any house cooling such as a swamp cooler?  If not, it
is possible to lower a tank's temperature by blowing air over the
tank's water using water evaporation to cool it. The fan need not be
very large.  I recall one  person used a computer fan.   Depending on
your fish population you may need to screen the top to keep "jumpers"
inside the tank.

I have a strange situation with one 10 gallon tank.  It is set up near
the "return" duct for my air conditioning.  It is the only tank of 5
that the tank temperature runs cooler than the room temperature.
Which brings me to a warning, I must keep an eye on the water level.
While the moving air cools through evaporation, that evaporation is
taking water from the tank and continually requires additional water.
This, in turn, concentrates the solids left behind making water
changes even more important so the solids don't build up.  (For more
google "old tank syndrome."

dick

The heater thermostat does not need to be turned down. A thermostat turns the
heater on when the water temperature drops below the set threshold. If the
room temperature is higher than the threshold then the water temperature will
not drop low enough for the heater to operate. If the water temperature DID
drop below 26 degrees then you DO want the heater to come on.

In short a thermostat is there to protect the fish's environment from low
temperatures; leave it alone.

200l has quite a significant thermal mass. What is just as important as the
max temp in the day is how low it gets at night. The best way to check is to
monitor the tank thermometer and see what temperature it gets up to and how
low it can get at night. You may find that the water temp only fluctuates
between 26 deg and 32 deg which'll be fine for most tropical fish.