Any problem with using 2 water heaters?

[hamstercaster]

Hi, right now I am using a 150 watt water heater for my 55g tank.  I bought the whole set up second hand and the previous user had no problems with his water temp dropping.  I do have this problem though.  If we turn down the heat in the basement for exemple, the water temp drops down by 2 degrees in a matter of hours.  I am close to winning a bid for a 200 watt heater on Ebay and was wondering if I could use both the 150 and the 200 watt heaters at the same time or will the 200 watt be sufficient?  The heater I am bidding on is for tanks that range from 18 to 53g.. mine's a 55g but since it's not filled all the way up I figure I only have about 50g of water. 

Would two heaters make the water too hot or will they work well together shutting off when the temperature reaches what I have set it up too on each their parts of the tank?  Or should I just use the 200 watt and see if it will be able to keep the temp stable no matter what happens to the ambiant room temp in my basement?

Thanks

[kennyman]

That little heater is working hard to maintain temperature and will likely fail sooner than later. Most recommendations I have seen suggest 4x-5x the volume of tank in watts of heater.

ie: 55gal x4=220w

Runing two heaters meens you have a backup when one fails. I run two in my 55 and it works they way you suggested.

[babblefish1960]

The short answer, yes, two heaters will keep the temperature more constant.

Now for the long answer: One of the issues with deciding what heater would work best to heat a tank of water is knowing what the ambient differential temperature would be.
Is the tank temperature range desired going to be very near the room temperature range?

If for example, you wish to heat a 10 gallon tank 5 degrees C above the room temperature, you would require a 25 watt heater. Make the room 10 degrees C colder, and you need a 50 watt heater.
You speak of a 55 gallon losing 2 degrees in a few hours, water by its very nature is a model of heat mass storage, so yes, you are turning down the room temperature far outside the ability of the heater to cope, and need to either stop that behaviour, or add a heater to even things up.
Two heaters in a tank are not unlike balancing carburetters in a car. the more you have, the harder it is to get them to work together. I recall tuning a holley six-pack way back and it takes time to get everything right.
Take some time to place the heaters properly, and ensure they are calibrated correctly, and then adjust them so that they both come on rather than just one all the time.

If the cold room issue is a winter thing, you may also want to consider some form of night insulation much the way you would for a pet bird. If you lower the room temperature and the tank cools off, you are asking you heat mass storage unit(aquarium) to heat the room for you instead, this is inefficient and pointless.
If you turn down the room temperature to save money on the heating bill, you will pay even more money for the electricity bill using the tank heaters instead.

If you are talking about a span of temperature difference of 20 degrees celcius or more, you are also talking about a pair of 250 watt heaters or even 300 watt to keep the tank reasonably stable.

In order to make a more accurate analysis of the situation, the temperatures of the two systems need to become known, what is the lowest temperature that the basement becomes, and what are the temperature requirements of the fish being kept?

[hamstercaster]

The short answer, yes, two heaters will keep the temperature more constant.

Now for the long answer: One of the issues with deciding what heater would work best to heat a tank of water is knowing what the ambient differential temperature would be.
Is the tank temperature range desired going to be very near the room temperature range?

If for example, you wish to heat a 10 gallon tank 5 degrees C above the room temperature, you would require a 25 watt heater. Make the room 10 degrees C colder, and you need a 50 watt heater.
You speak of a 55 gallon losing 2 degrees in a few hours, water by its very nature is a model of heat mass storage, so yes, you are turning down the room temperature far outside the ability of the heater to cope, and need to either stop that behaviour, or add a heater to even things up.
Two heaters in a tank are not unlike balancing carburetters in a car. the more you have, the harder it is to get them to work together. I recall tuning a holley six-pack way back and it takes time to get everything right.
Take some time to place the heaters properly, and ensure they are calibrated correctly, and then adjust them so that they both come on rather than just one all the time.

If the cold room issue is a winter thing, you may also want to consider some form of night insulation much the way you would for a pet bird. If you lower the room temperature and the tank cools off, you are asking you heat mass storage unit(aquarium) to heat the room for you instead, this is inefficient and pointless.
If you turn down the room temperature to save money on the heating bill, you will pay even more money for the electricity bill using the tank heaters instead.

If you are talking about a span of temperature difference of 20 degrees celcius or more, you are also talking about a pair of 250 watt heaters or even 300 watt to keep the tank reasonably stable.

In order to make a more accurate analysis of the situation, the temperatures of the two systems need to become known, what is the lowest temperature that the basement becomes, and what are the temperature requirements of the fish being kept?

You hit it on the nail.  My wife turns the thermostat down overnight to save money on our heating bill (electricity bill).  She's always been like that.  She has a constant fear of going bankrupt lol.  I would say that there is a 5-7 degree difference between the basement's temperature and the water temperature.  I will advise her to keep the heat up in the basement and see if the heater will keep up.  It does seem to come on on a somewhat regular basis but not for long spurts of time though...  The first week we had the tank, the water temparature was very stable and she did not play with the thermostat.  I may still go ahead and buy the 200 watt to be on the safe side and to make sure my heater doesn't work as hard but will most definitly take your advice on the use of two heaters.

Thanks for the answers, they are once again very helpful