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I have two 100-watt heaters in a 55-gallon tank. Annoyingly, no matter how I set the heaters, one heater is consistently carrying all of the load and the other just stays off all the time. (It's a different heater based on how I set them; both of them work.) If the heaters had perfectly-calibrated thermostats, then it would be easy to avoid this problem, but that just isn't the case.

Should I care? If so, what should I do about this?

The only way I know of to make two heaters work as one unit in a tank (to truely synchronise them) is to run them from one controller.

There is a great explaination here:

http://www.jehmco.com/PRODUCTS_/HARDWARE_/Temperature_Controller/body_temperature_controller.html

EDIT: And yes, you should care. As the info at the above link explains, making one heater work overly hard increases the likelihood of premature failure.

Been there, experienced that on a 90 gallon tank. The heater failed while away on holiday. The fish sitter did not notice until it was too late. Ultimately all inhabitants died - most apparently died directly from the heat, others ultimatley succumbed to the bacterial infections which followed. Devastating. The tank sat empty for nearly three years before my heart healed enough to restart...

Last edited by heaven2 at 23-Oct-2004 23:07

Silverlight

Heat some water in a small container deep enough for your heater. Check it with a thermomenter then try to adjust the two heaters seperatly.

It also could depend on the location of the heaters in the tank as well.

Keith

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It also really depends on how many watts your heaters are. If the one heater that is running all the time is 300 W. Your fine and the other one will act as a backup. If your running two 150's you need to follow the advice given in the previous posts. Hope this helps.

The heaters are each 100-watt, so just one is almost certainly getting overworked - seems to be on about 80% of the time. I already had a spare 100-watt Ebo Jager, so I got another one to match it and put them at opposite ends of the tank, vertically.

The controller idea isn't a bad one, but I would rather have gotten a 200-250 watt heater, used it as the main, and set the 100 a few degrees lower as a backup.

i run 2 rena cal 200 watt heaters in my 75g tank. i also tried to do what your doing and i tell you it took me months but IT IS POSSIBLE. there are many things that effect them so you need to sepperate them as much as possible. leave them over night after the move then look over once in a while see whats on and whats not. my rena cals can adjust 1ºf a time but even this isnt perfect. best to go about this blind, other words dont look at the dial it doesnt work anyway in being accurate. mine are set at 72º and 78º and my tank is stable at 79º lol. anyway watch the temp of the tank and the heaters. get them set close enough so you see them on at the same time once in a while. get to this point and you really close, prolly off a half a degree which you cant adjust of course. make sure the heaters see the same amount of current and ar at exact hight. also the angle must be identicle of the heaters. looking for mirror images. if they still dont act 90% of the same mess with the hights. usually the tank varies in temp at the top compared to bottom so if one heater is still off try raising it a inch. make sure to wait 24 hrs before any adjustments. eventually you will get them to run almost identicle but never perfect. mianly because there is allways temp changes in the tank and what happens to one side might not allways be happening on the other. currents in the water and in the air around the tank effect temps. decor effects current so one heater may see more water turn over then another. you got a fight ahead of ya but it can be done i promise i wish ya the best of luck.

Sin