heater for a 45gal, 24" high tank - Tropical Fish Keeping - Aquarium fish care and resources
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post #1 of 3 Old 03-22-2011, 11:11 AM Thread Starter
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heater for a 45gal, 24" high tank


I am writing this in desperation because I have had heater problems almost since the installation of my tank in August 2010. It's stressing out my fish and I've lost several to disease (first ich, now something I cannot identify).

Here's the situation: I have a moderately-heavily planted 45-gallon freshwater tank that is 24" high and powered by an HOB Marineland filter. It houses cardinals and corydoras. I installed a 300W Marineland Visi-Therm heater in August and monitored its function...I set it at one temperature and put a thermometer in one corner towards the top. The temperature of the water was consistently below the temp setting on the heater, even when the light was off. I contacted Marineland's customer service and they promptly replaced it.

I installed the second one. It seemed to better for some time. Then one nigh in the middle of the winter (house ambient temp around 56 degrees), the temperature dropped. I woke up and the tank water was the same as the ambient temp and the heater was off. I still had the old heater, so I stuck that one in hoping that 2 300W heaters might keep the temp stable. I also kept the ambient at 66 degrees even at night after this incident. This method wasn't terribly efficient - I set both heaters to 80 degrees and the water stayed around 78. So I raised it to 82 to get a water temp of 79-80...at least it was stable. (I lost 9 cardinals to ich a few weeks after the first heater "failure").

Then, recently I had another temp drop - it dropped to around 70 degrees. This happened during the day, and I found out in the afternoon when I was doing a water change. By this time I had bought another heater but I had not installed it because the other two seemed to be working ok, albeit not perfectly. This heater is a Hydro or something like that...can't recall the exact name, but it's also a 300W heater I believe. So, I replaced the original Visi-Therm with the brand-new Hydro. Even still, I'm seeing another outbreak of infection of some sort (not ich...not sure what it is) in 2-3 cardinals and a cory. My water levels are good - nitrates always under 10; usually under 5; ammonia and nitrite 0; pH stable at 6.6-6.8 and soft water.

Both heaters are placed horizontally in the tank, one is up a little higher and towards the left, the other a little lower and towards the right. I still have the same problem with inaccuracy - the thermometer combo seems to be precise (it keeps my water at 80), but not accurate (they are both set to 82).

So, I need some advice on a better heater setup for this tank. Why am I having all these problems? I know water circulation might be a problem - it's a tall tank with an HOB filter. But actually, it would be ideal if the upper half of the tank were hotter than the lower half (cardinals like it a little warmer than corys). The Visi-Therms have gotten great reviews on here so I can't believe it's heater malfunction. I want to buy an Eheim Jager heater (I had one of these 8 years ago and I never, ever had problems...it still works but I am hesitant to use it because it looks like it has a crack in the glass, probably happened in storage.

One of the issues I am trying to consider is the proxiimity of the heater to plants - they can't move themselves and I don't want to burn them - thus the reason for keeping the heaters horizontal and up high (even though they are visibly not so pretty).

So...advice? What changes can I make to heat my tank accurately and precisely? This temp fluctuation is stressing my fish.

Thanks in advance for your help and advice, as always.
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post #2 of 3 Old 03-22-2011, 04:33 PM
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There is probably not a single heater on the market that will consistently keep the temperature at 80 degrees if you ambient room temp is 56, they just aren't made to do that. 10-15 degrees above ambient is what they can realistically do. That being said I honestly cant think of any reason that two 300watt heaters wouldn't heat a 45 gallon at 80 degrees, unless they are faulty or damaged.
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post #3 of 3 Old 03-23-2011, 08:57 AM Thread Starter
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Thanks for the response! Yes, I don't know why I thought that if I used a higher-wattage heater that it would be able to keep the tank higher above ambient than a heater of the wattage recommended for my tank. I guess I should have guessed that the relationship isn't linear, and is probably much more complicated than I assumed (physics wasn't my greatest subject...although I did enjoy it LOL!)

I guess I finally decided to write a post when the second temperature dip happened. I have the ambient temp set to always stay within 15 degrees of my desired tank temp (thought that would fix the initial problem and allow me to use just the one 300W heater).

I feel like two 300W heaters should be overkill for a 45-gallon tank, even if it is 24 inches tall and heavily planted. But, on the other hand, I can't believe that I got 2 defective Marineland Visi-Therm heaters, with all the good reviews they have! I keep thinking about the old saying, "A poor workman blames his tools" and wondering what I must be doing wrong. I must be missing something...

Maybe just for kicks I will get a bunch of internal thermometers and stick them in every corner of the tank - high and low - and see how the temps differ...at least for a start on understanding the problem.

Thanks so much for your input!!! I really appreciate you taking the time to respond!
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