When I had multiple smaller tanks for smaller fish, years ago, I used a lot of visitherms, had no big problems with them. They're maybe the best of the inexpensive heaters. They don't appear to have changed at all in 20 years. They're easier to break than the Jagers, however. The price delta for Jagers was huge back then.
Bob Garside of Upper Canada Discus says that the Sera heaters are also good, and I believe him. Their market penetration in the US isn't very strong, so they're hard to find, unfortunately...
Calibration has always been an issue wrt aquarium heaters. For most fishkeepers, it's not a big deal- just compensate with the setting. At the higher temps most people use with discus, it's sometimes problematical- when you turn the dial all the way up and the actual temp is 80F, well, that's no good.
Your new Jager may need calibration, tech- just follow the instructions I set out earlier if it does. Not really a big deal, at all.
Hey Guys 'n' Gals,
Can any of you recommend where to get the Eheim Jager heaters online for a good price? I looked around a bunch of LFS within driving distance of my house and those few that that do stock them are charging crazy prices. I usually do my own online searches, but you lot always seem to find better deals than me on just about everything...
Colin
I think Jagers are more efficent than many other heaters with higher wattages as well. Example: I have a 150 gal. that has 2- 250 watt Jagers in it. I have no problem keeping any temp. I want in it. In fact, I feel I could get away with only one of the heaters in there, although one would not be nearly as efficent at higher temps., and would probably stay on most of the time. This tank use to have a 500 watt titanium heater on a Ranco controller. It worked, but was not nearly as efficent, and had a harder time keeping a steady temp. It always bounced around a couple degrees. The Jagers are much better. When the 8 year old controller crapped out, in went the 2 new Jagers. Should have done that years ago.
Darrell
All electric aquarium heaters are basically 100% efficient, with current being converted directly to heat. They're just big resistors.
OTOH, there are lots of different ways to configure resistors. Jagers, for example, are a single resistor, with lower resistance for higher wattages. We can see that thru the glass, one continuous wire wrapped around a ceramic core. Some other heaters may not be set up that way- they could be using two 250W resistors in parallel to get 500W total output. In that scenario, one resistor might be open while the other is working fine, so real heat output would only be 250W. It's impossible to tell about the titanium heaters without tearing them apart... but the current draw and therefore the heat output of any resistor can be obtained using an ohm meter and some basic math.
There are also issues wrt differential, or hysteresis. With conventional bimetal thermostats, the switch points are closed during heating, and then snap open, stay open until they cool off, then snap shut and the cycle repeats. The difference in temperature is the differential. This process is also affected by the thermal mass (latent heat) of the element and associated hardware. With heaters having a lot of mass, the temp of the heated medium will go up slightly even after the element is turned off, as the heat equalizes. This increases the differential. Even electronic thermostats generally have a differential of at least 1F.
Too little differential is hard on the thermostat, because it cycles more often than with a larger differential, wears out faster. Too much is not good for the fish. Water itself has huge thermal mass, unlike air, so it tends to be more stable temp-wise, harder to move in any direction.
What that all translates into is that aquarists should use the smallest heater that will maintain to proper temp with minimal cycling in their given situation. If your house is kept at a very constant temp, day and night, then you can use a smaller heater than if you let the room temp sink at night. If your tanks are insulated and have tight fitting tops, you can use smaller heaters. If you turn down the house thermostat when gone on a winter vacation, you'll want heaters that can pick up the additional load... Lots of variables, but it's easy to oversize heaters, which turns into a big problem very quickly if they fail on... It's tough to be wrong if the usual recommendation of 3-5W/gal is observed...
Part of what I do for a living is HVAC work, and a lot of that knowledge transfers from air to water directly...