Habitat - Indoor :: Heater

[ljapa]

Two different brands? Or did you buy the same kind?

Same brand, but different sizes. My thought was just that one might fail, and better to have a backup.

[steve]

@ILoveRocky - you didn't need a receipt, d'oh!

@cutepanda86 - oversized one is not a problem BUT I would measure it's length since some of them are pretty long. It also depends on your room temperature, however since Sheldon is an adult, I think he would be OK with a 75W. According to FosterSmith, the 75W is 10" long and for 16-26 gallons. If you plan to fill it up, get the 100W.

@ljapa - I agree. I've had the Visitherms fail both ways, and a Jager off.

[cutepanda86]

@cutepanda86 - oversized one is not a problem BUT I would measure it's length since some of them are pretty long. It also depends on your room temperature, however since Sheldon is an adult, I think he would be OK with a 75W. According to FosterSmith, the 75W is 10" long and for 16-26 gallons. If you plan to fill it up, get the 100W.

Thanks for the advice Steve. I appreciate it.

[vear]

The Eiheim Jager specification says I need a 150W model for a 75gal. Not really even close to the 3-5W per gallon rule. What do you guys think?

[ljapa]

The Eiheim Jager specification says I need a 150W model for a 75gal. Not really even close to the 3-5W per gallon rule. What do you guys think?

A higher wattage heater will draw more power when on, but because it is larger, any surface on it will not be hotter than a lower wattage. To heat water, you're just dumping energy into it. The amount of energy you need to dump to raise a set volume of water a set number of degrees is the same whether you are using a small heater or a large heater.

In terms of the watt-hours used to heat and keep the tank at a set temp, it's the same, no matter the size. A larger heater doesn't run as often. A heater too small can't dump out enough energy to make up for the heat loss and never shuts off or reaches your target temp.

I figure since the electricity costs are identical, large is better and gives you a cushion.

There's no definitive formula for size because the other factor besides water volume is how fast the aquarium loses heat. Don't have your aquarium top closed with glass lids? You're losing heat through evaporation. (The water molecules that leave through evaporation are the ones with the most heat energy.). Have a room that's at 65 instead of 75? You're losing heat faster through the sides of the glass, the filter and tubing, as well as evaporation. Have the a/c going so the air's not only cooler but dryer? You're losing heat to evaporation faster than if the humidity is at 95% and almost no evaporation is happening.

For an analogy, imagine a 5 gallon bucket. The water level is the temp. There's a line in it that is your target temp. Any time the water level is below that line, your heater is on. Any time it is above that line, it's off.

There's a hole in the bottom of the bucket. That's your heat loss. If your basking area is in the tank, you have a cover with holes cut just for the lights, you have thick glass and a warm humid air temp, that hole is really small. If you have an ATBA with no covers at all, an a/c keeping the temp cool and the humidity low, that hole's pretty big.

Your heater is a faucet above the bucket, but it's not like a normal faucet where you can turn the knob and control the flow. Instead there's an on/off button and the water comes out at a fixed speed (the wattage of the heater; the higher the wattage, the faster the water comes out).

Whatever the size of the hole (heat loss rate), once the water level (temp) drops too low, the faucet kicks on at its fixed rate (your X wattage heater turns on). If that faucet rate is fast, it quickly fills back up to your line and turns off. If it's slower, it takes longer to reach the line. If it's slower than the hole, it can never make it back to the line and you have a heater that's too small.

Of course, the hole size isn't fixed. As your tank temp drops and gets closer to ambient temp, the hole gets smaller. As the humidity in the room varies, so does the evaporation rate.

If you're heating a 10 gallon tank, your bucket is smaller than if you are heating a 125 gallon one.

I say oversize a bit, if you can fit the larger heater. Don't go too big, because it does take time for the heat to diffuse. You can help that by putting the heater so it gets hit by your filter outflow.

[vear]

The Eiheim Jager specification says I need a 150W model for a 75gal. Not really even close to the 3-5W per gallon rule. What do you guys think?

A higher wattage heater will draw more power when on, but because it is larger, any surface on it will not be hotter than a lower wattage. To heat water, you're just dumping energy into it. The amount of energy you need to dump to raise a set volume of water a set number of degrees is the same whether you are using a small heater or a large heater.

In terms of the watt-hours used to heat and keep the tank at a set temp, it's the same, no matter the size. A larger heater doesn't run as often. A heater too small can't dump out enough energy to make up for the heat loss and never shuts off or reaches your target temp.

I figure since the electricity costs are identical, large is better and gives you a cushion.

There's no definitive formula for size because the other factor besides water volume is how fast the aquarium loses heat. Don't have your aquarium top closed with glass lids? You're losing heat through evaporation. (The water molecules that leave through evaporation are the ones with the most heat energy.). Have a room that's at 65 instead of 75? You're losing heat faster through the sides of the glass, the filter and tubing, as well as evaporation. Have the a/c going so the air's not only cooler but dryer? You're losing heat to evaporation faster than if the humidity is at 95% and almost no evaporation is happening.

For an analogy, imagine a 5 gallon bucket. The water level is the temp. There's a line in it that is your target temp. Any time the water level is below that line, your heater is on. Any time it is above that line, it's off.

There's a hole in the bottom of the bucket. That's your heat loss. If your basking area is in the tank, you have a cover with holes cut just for the lights, you have thick glass and a warm humid air temp, that hole is really small. If you have an ATBA with no covers at all, an a/c keeping the temp cool and the humidity low, that hole's pretty big.

Your heater is a faucet above the bucket, but it's not like a normal faucet where you can turn the knob and control the flow. Instead there's an on/off button and the water comes out at a fixed speed (the wattage of the heater; the higher the wattage, the faster the water comes out).

Whatever the size of the hole (heat loss rate), once the water level (temp) drops too low, the faucet kicks on at its fixed rate (your X wattage heater turns on). If that faucet rate is fast, it quickly fills back up to your line and turns off. If it's slower, it takes longer to reach the line. If it's slower than the hole, it can never make it back to the line and you have a heater that's too small.

Of course, the hole size isn't fixed. As your tank temp drops and gets closer to ambient temp, the hole gets smaller. As the humidity in the room varies, so does the evaporation rate.

If you're heating a 10 gallon tank, your bucket is smaller than if you are heating a 125 gallon one.

I say oversize a bit, if you can fit the larger heater. Don't go too big, because it does take time for the heat to diffuse. You can help that by putting the heater so it gets hit by your filter outflow.

This was really helpful, thanks for taking the time to write it out!

[cutepanda86]

This was really helpful, thanks for taking the time to write it out!

It was very helpful! Thanks!

[devilduck]

Great post, this question is for DevilDuck. I also have a 55 gallon tank but not filled to the top. Its filled a bit higher than midway. I had to get rid of my heater because it started to make popping sounds, and when i googled, I found out it had been discontinued :/

I want to get the heater you have eheim jager, my question is how come you have so many wattage usage? should I get that much, my last heater was just 100 watts, and it heated fine. Is the eheim jager weak in heating?

Thank you

Only because they were on sale at Dr.s Fosters and Smith. In hindsight, I should have gotten a smaller one because the eheim I have is a little too long for my tastes. Getting a little higher wattage heater won't hurt, it will just reach the set temperature faster.