Regarding the Rena Cal Top Light Excel Heater

Question
QUESTION: Hi Fish Deeva,

I have a 38 gallon fish tank with guppies fish and I am using 150 W heater for about almost 1 year now. But, all of a sudden yesterday the water temperature went really high about 88F. So, I am just wondering if the heater is overheating the water because I set it up at 77 F. So, soon as I saw that I unplugged the heater for abut 20 minutes and I changed the water in the tank to the same temperature as in the tank. After, I plugged in the heater and cheked the water after 8 hourse and it's went down slowly now it's staying at 79F for almost 6 or 7 hours and didn't go up after that. So, I am just wondering if I should buy a new heater. Since, I do not have that much experience and I will be happy if you could provide me any feedback on this. Thank you so much.

ANSWER: Hi Tharani,

It could be the heater, but please don't assume that.  My guess is it's lighting or the tank's lid not allowing air to circulate.  Take a look at that while you're at it, just incase. :)  Let me know how it goes.  We can always brainstorm to try to answer this question.

Happy fish-keeping.

---------- FOLLOW-UP ----------

QUESTION: Thank you for responding to my question. The tank has been running for more than 1 year now and before I had goldfish but then I had guppy for almost 1 year now. So, the heater was working in the tank for almost about 1 year and I have placed the heater near the filter where the water flow continusely and the filter is a very good filter (Auqa Clear). And the lighting system in the tank is fluorescent so it does not heat the tank water. I did not have any problem with the temperature until yesterday. I noticed the heater before, its usually turn the light on while it working for about 1 or 2 min and the turn off automatically and the turns once in a while. But, from yesterday I noticed the heater the light turns on and stay for a while for about 15 to 25 min and then turn off. Also, the temperature stays at 78 or 79 but after the heater turns on it goes to 80 and after the heater turns off it comes back to 78 or 79 and then the heater turn on again and the tempeature goes to 80 again. Before I didn't had this problem it's always stays at 79 and doesn't go up or down. Thank you so much.

ANSWER: Hi,

It's dangerous when a heater begins doing that.  It's caused by corrosion on the thermostadt inside.  Time for a new heater and yes, you are probably right.  It's the heater.  I'd take it out. :)

Happy fish-keeping

---------- FOLLOW-UP ----------

QUESTION: Thank you so much for your reply. I am thinking about buying a new heater as well. But, do heater usually fail in 1 year. Eventhough, the tempeature didn't go beyond 80 for about 2 days but I have fluctuation in the temperature as I told you it goes 78 or 79 and then when the heater turns on goes to 80. Usually, heater light doesn't stay on for long as 15 min or more and my room tempeature is between 74 to 76 so there is no need for the heater to be on for long time. So, you want me to unplug the heater immideately and buy a new one because I am thinking of going to the pet shop in the evenning but if you say it's dangerous I am thinking about going in the morning. Also, I have a question when you set a heater at a certain temperature eventhough I usally set up my heater at 77F it goes to 79 and stays there without any fluctuation. So when you usally set a heater at a certain temperature and if the desired level is reached it should stay in the same temperature throughout isn't it without any changes in the temperature if the heater is working properly. I really appreciate you for your reply. Thank you so much once again.

Answer
It is very abnormal for a heater to fail in a year, so I would consider contacting the company who made it.  There are telephone numbers listed online for that.

A little fluctuation in temperature is normal.  You might try setting it to 75 (which is fine for most types of fish), and seeing if it fluctuates.  Remember that fluctuation.  In the wild, water also fluctuates somewhat, so fishes can do okay like that.  

I would be careful using it if it ever goes above 80 without being set within 2 degrees of it.  

I woke up one morning to boiled fish.  I lost hundreds of dollars worth of fish, but not only that, I lost my beloved snail, who was about 2.5" across...Speedy.  He would climb the air line tubing, and would fall down in the bubbles all day.  He was a total ham.  He actually had a personality.  When I woke up to fish/snail soup, the smell was worse than anything you can imagine.  What had happened, is the heater had gone up during the night, and had hit 90.  Even at 90, the water was so gross, and the fish died horrible deaths.  I would caution you that if your heater ever fluctuates more than 2 degrees either way, to replace it rather than to risk it, because I have lived it, and it's an awful ordeal.  I had those African Cichlids for many years.  Many had names and were tame.  What a sad loss...enough said. :)

88F is certainly deadly to the fish.  If it was set at 79 and went to 88, that's really a jump not worthy of keeping that heater.  I would never trust it again, personally.

Happy fish-keeping.