Can I use under-rated heater?

[dwiles]

Hi guys, I have a 330 litre tank I have set up recently.
I was given a free 200w heater a little while ago, which is said to be rated for aquariums up to 250 litres, it has a built in thermostat.
I set up the tank last week and used this heater, I set the temp to 28 degrees C (as I am eventually getting discus).
However since then, 5 days on, the tank has only risen to 25 degrees C (even though it keeps turning itself off - the thermostat must be faulty).
To combat this I have set the temperature way over to around 34 degrees C, my temperature now is reading more around the 27 degrees mark - close to where I want it.

So my question is; can I leave the heater to operate like this? Being set over what I need it to compensate for its lacking in size, in order to get my desired temperature? Or should I stop being a cheapskate and just buy the right sized heater?! Thanks in advance

 

[Seanthebusdriver]

The thermostat isn't faulty its just reaching the temperature that you have set it to in the water immediately around the heater. Discus need the temperature to be nearer 30 centigrade and unfortunately your heater is unlikely to ever achieve and hold that temperature as the ambient room temperature rises and falls. You could buy another low wattage heater at a lower cost and run 2 heaters or take the plunge and buy a heater for your requirements.

 

[Byron]

A couple of suggestions. First is, that in this large a tank, you should really have two heaters, whatever the wattage. The best placement is at opposite ends, and beside the filter intake and return (which would obviously be at opposite ends whenever possible). This provides water flow around the heater, one as water enters the tank and the other as it leaves.

Second, concerning wattage, I would use both your 200w heaters on this tank (330 liters, or roughly 87 gallons). Heaters of 250w or even 300w would be good, but the 200w should work. I have two 200w heaters on my 4-foot 70g, and used to have the same on my 5-foot 115g.

Third, heaters do not always heat true to the set temperature. Provided the temperature remains stable, this is not a problem. Example, I have an Eheim Jager heater in my 33g that keeps the tank at 24C./75F, though the set temperature on the dial is 70F. When adding a heater, have the tank water at the temperature you want it to remain, and then after the heater is plugged in for several minutes adjust the dial accordingly (usually this means until the heater turns on or goes out). Monitor it for several hours to ensure it is properly set, to avoid over- or under-heating. However, I think your have an issue here--your difference is rather large, but this most likely has to do with the single heater in so large a volume of water. It is basically overworking. Remember that the cooler room temperature (assume this is so) will continually be affecting the tank water temperature down, at the glass surfaces farther away from the heater. Using two heaters at opposite ends should solve this.

Fourth, the ambient room temperature is very important. Aquarium heaters are not intended to maintain warm temperatures in a cold room, and this can easily cause them to malfunction. A difference of around 10 degrees F (approximately 5-6 degrees C) is the most it should be. In my fish room for example, the ambient room temperature in the winter is 70-72 F, and the tank heaters keep the tanks around 75F (one is 80F). The closer the ambient room tyemperature to the aquarium heater set temperature, the less the heater will have to work and this means longer life and more reliability.

Byron.

 

[ShinySideUp]

While Byron is right regarding using two heaters when I tried it I had trouble balancing them and found that one came on every time and the other hardly at all. I used two 200w heaters in a six foot tank (in a warm room) but eventually gave up and now use 1 x 300 watt heater in conjunction with a Koralia pump to drive warmed water along the bottom and into the flow from the FX5 filter.

The crucial thing is, as has been said, in a cold room more than one heater is necessary but I find in my warm room 1 is sufficient. In fact I often forget to turn it back on and the temperature drops at night to about 25C as opposed to staying at 28C with the heater on so not a big deal...

...which reminds me, I did a water change today and forgot to turn the heater on; must go now!

 

[dwiles]

Thats great thanks for the advice! My room is always pretty warm, but I will add my other heater from the holding tank once I have moved the stock over and do as you say - calibrate both accordingly to get my desired temperature (the dealer that I am getting the discus from keeps them at 28 Centigrade). Thanks again.

Dan

 

[Byron]

Thats great thanks for the advice! My room is always pretty warm, but I will add my other heater from the holding tank once I have moved the stock over and do as you say - calibrate both accordingly to get my desired temperature (the dealer that I am getting the discus from keeps them at 28 Centigrade). Thanks again.

Dan

Discus need warmth, and 28C (82F) is fine. And definitely both heaters, you do not want discus chilling.