Tank not heating properly

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vtnamezeboi

Plecostomus
MFK Member
Sep 7, 2005
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I have a 150 gallon with a 300 watt heater. It use to be set at 85 and will hold the tank around 82. after a year the tank will drop to 79-80 constantly so i added another 300 watt heater. I started the new heater at 82 and tank still sits 79-80 so then I slowly cranked up the second heater and now its set to 87 and fish tank will sit at 79 still. Any idea whats going on? I know the heaters are working cause at night I can see the coils in the heaters light up.
 
What's the ambient room temp? What brand of heaters? Is this a glass tank? Did you actually wrap your fingers around the heater where the coils are? It won't burn your hand since the surrounding water is cooling the heater at the same time. I do this to check that the heaters are actually working.
 
Just because the lights on doesn’t mean the heater is working. Put your hand on it to make sure it’s hot. There’s also a few other factors. If you don’t have proper circulation inside your aquarium you could have hot and cold spots. Depending on the make of the heater the size of the coils are different size on the same wattage.
 
What are you using to measure the temperature of the tank? Where is the thermometer in relation to the heaters?
 
What's the ambient room temp? What brand of heaters? Is this a glass tank? Did you actually wrap your fingers around the heater where the coils are? It won't burn your hand since the surrounding water is cooling the heater at the same time. I do this to check that the heaters are actually working.
My room temp is 74 degrees. Brand is eheim. Glass tank. Yes I touched them. I can feel the warmth. I’m wondering if putting them in my overflow is a bad idea.
 
My room temp is 74 degrees. Brand is eheim. Glass tank. Yes I touched them. I can feel the warmth. I’m wondering if putting them in my overflow is a bad idea.

You may be losing too much heat that way. Have you observed the new one going on? I have 2 eheim 300 watt heaters for my acrylic 240g, and it takes 1 hour for it to raise the temperature by 1 degree (from 75F to 76F) in a room that is 69F. My heaters are in the tank, and I have a heater controller that turns both heaters on at the same time and turns them off at the same time.

Have you calibrated the heaters in a 5 gallon bucket?
 
Given you are trying to heat this 150 gallons less than 10deg above ambient, 600 watts worth of heaters should be able to easily do the trick.
 
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