Safely change heater?

[BillD]

Stick on thermometers may read slightly below the actual water temp, since the measure the temp of the outside of the glass. If the floating thermometer says 80, that is what it is, within the accuracy of that thermometer. What you have dialed on the heater isn't really significant as long as it maintains the temp you want. As well, minor fluctuations in temp aren't really a concern.

 

[evil Nick]

Stick on thermometers may read slightly below the actual water temp, since the measure the temp of the outside of the glass. If the floating thermometer says 80, that is what it is, within the accuracy of that thermometer. What you have dialed on the heater isn't really significant as long as it maintains the temp you want. As well, minor fluctuations in temp aren't really a concern.

went home at lunch. What I had dialed was apparently 86... wow.
Was barely at 80 though and the things wasn't running. My guess is this one might be defective so I contacted amazon and there is another on the way.
I can still use my old heater since its still in the tank if this drops below 80.
My ambient room temp is like 60-62 during the day since the furnace isnt running unless it gets below about 50. Either way though the heater should be keeping the water at what is set. I bought this one cause it goes up to about 95 in the settings. I wanted something I could pump up if heat treatment was needed.

I figured the stick on was off since it was also measuring ambient room temp.

 

[PNWaquarist]

Give it a good 24-36 hours. It takes a while to warm 50 gallons of water, and your cold ambient room temperature is undoubtedly slowing the process.


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[dalto]

A 200w heater may not be enough to heat your tank 25f from room temp. Heater sizing is totally dependent on ambient room temperature and depending on your exact tank size and dimensions 200W is really pushing it.

 

[jetajockey]

It's not unusual for heaters to be off by a few degrees, nearly every one I've had has been.

 

[evil Nick]

A 200w heater may not be enough to heat your tank 25f from room temp. Heater sizing is totally dependent on ambient room temperature and depending on your exact tank size and dimensions 200W is really pushing it.

This is rated for a 50 gallon. I only have a 29. Any bigger of a heater and I may risk burning it out. It says the heater will go to 95 on the temp setting. I had it maxed and it was barely coming on at 78 degrees.
It also wasnt heating from ambient room it was replacing my old heater which altready had the tank stable at 81.
The heater was on ALL night after I did a slow change between the two and when I went home after work the tank dropped to 75! Thank god my fish seemed okay and actually almost seemed happier. Either way My old heater is back on and holding the temp fine and a replacement is on its way for the new one.
I think the thermostat in the new one was funky. It didnt seem to ever want to turn on until I manually increased the temp even though the tank temp was dropping.

as for being off by a few degrees, I expect this but not TEN lol.

 

[PNWaquarist]

Yeah, sounds like a dud. I have a 150 W Hagen Marina on my 29. My house is usually 68 F at this time of the year and, when I set the heater to 72, my water temp is 77.


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[dalto]

I only have a 29.

The calculation would be different. The ratings don't really account for a heating differential as large as you have. Also, the shape and thickness of the tank itself make a big difference.

Here is a calculator that seems to do a good job of taking all those factors into account.

Aquarium Heater Calculator

 

[PNWaquarist]

Very useful link. Thanks for sharing.

 

[evil Nick]

So should I have gotten the 300watt?
I came home today and my old. Heater was not running for so!e reason and my tank was down to 70. I plugged back in the new one and fiddled with the old ones knob until it turned back on. What is going on!
Maybe I should be running both for the winter in this tank

I did the calculator and even for a TWENTY degree difference it says 200 watts is perfect. I got a dud in the new one and I think the old one may have overworked and overheated.

New replacement is in tomorrow

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[PNWaquarist]

How long has your house been in the low 60s? It may be that your current heater(s) can't handle the current temperature difference. Don't get a 300 W heater. That's way too much juice for your tank.

See how things shake out with your new 200. If it's struggling to keep your tank at 80 or whatever the desired temp is, I'd go with the 200 W and one 50 W. The 200 W would run all of the time and you could use the 50 W concurrently when your house gets cold in the late fall/winter.

Also, research and get the best-performing and most reliable one(s) out there.