Temperature And White Cloud Mountain Minnows

[Kaidonni]

The past week I've been thinking about my three White Cloud Mountain Minnows and the temperature in the tank.
 
Tank is ~50 litres when full (I'd reckon about 46-48 litres as it is with the filter, heater, airstone and plants). Tank lighting is Sun-Glo 46cm 15w T8, on for 6 hours a day from 2pm to 8pm, and it has been in use since March this year. The temperature goes up to ~23.5C when the light is on. This morning it was down to 21.5-22C, and my father checked it while I was at work, reporting 21C. This is with the thermostat on the heater set to the line after the 19 mark; it actually goes something like |19| |22|, and it can be set either on the numbers, in the blank areas, or on the lines - not very intuitive! The thermostat does go above 22C, but I don't think it's of any consequence as I wouldn't be turning it up that high anyway. At the moment, this means the tank is experiencing a daily fluctuation of ~2.5C (that's if it doesn't go any lower than 21C) - is that fine for the White Cloud Mountain Minnows, seeing as their optimum range is 18-22C? Is that fine fullstop, regardless of fish species? Should I be allowing a fluctuation of this size, or a fluctuation at all?

I won't be going for an LED light, so I don't really think that I can avoid the temperature going above 22C due to the light itself. I could set the thermostat higher to minimise the fluctuation - but then the higher I set it, the closer it will be to 22C at it's minimum (the maximum optimum temperature for White Cloud Mountain Minnows).

 

[Byron]

There are a couple of things to keep in mind when discussing temperature.  The first is that stratification is normal in an aquarium; a filter sufficient for the tank is likely not going to prevent this, nor should it need to.  This is normal in every water course with few exceptions.  And warm water, like warm air, rises, and cold sinks.  So the water at the surface will probably be warmer than lower down.  Depending where you have the thermometer, take this into account.  And at the next water change, when you start, slowly lower your hand straight down and you will likely see what I am talking about.  The other thing about this is that fish will move to cooler water if they feel the need.
 
Second, a difference of 1 or 2 degrees C is not going to matter over the course of the day/night.  Here again, we have something very natural in almost all habitats...the water tends to cool during darkness.  Some aquarists actually advocate two heaters on timers; one with a higher setting that will only be "on" during the day, the other with a lower setting that comes on during darkness just to avoid too low a drop.  This is more important for some fish than others, and also depends upon your climate and house temperature day and night.
 
And the temperature of the tank will not be below the room temperature for extended periods.  If the room temperature suddenly rises significantly, such as in the morning when one might turn on the furnace, it will take the tank longer to increase temperature, but it will.
 
On the heater setting, I would find the setting that brings the heating element on when the temperature is as low as you would want it.  Chances are this will rarely be reached, unless again you are in a very cold winter climate with an unheated house/room.  The species mentioned here are cooler water so this is not likely to be an issue.
 
Byron.

 

[Kaidonni]

Thanks for the reply.