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Hydor 25 Watt Adjustable Heater

731 Views 10 Replies 5 Participants Last post by  tlriot
I have a Hydor Theo 25 watt heater in a 2.5 gallon tank right now. It's going to be moved into a 5g, but while I'm using it the readings seem off. Its been running almost a week, so it's brand new. My digital thermometer is reading between about 82 and 79 degrees, but the heater is set to only 75/76.

Is this just because the tank is so small or could something be wrong with the heater or thermometer? It stays pretty stable and only fluctuates from day to night from the added heat of the CFL.
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Do you have another thermometer you could check it with? A non-digital one maybe?
No, but I was going to pick one up tomorrow and check it.

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You will very rarely find an accurate thermometer, much more so in the low Wattage units. As long as yo can adjust it till it holds the temperature you are aiming for and stays there, it should be fine.
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In cheap thermometers, it is rare to find the correct one. My method when buying off the shelf is to look at a number of them and choose one that reads near the center of the group.
One item that I do find really important and very true for small tanks is protecting myself. Heaters are one of the most failure prone items and they can kill quickly in small tanks as the temperature swings so easily.
I highly recommend using a temperature controller as a backup safety in case the heater stick on.
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That was sort of what I thought. My house also does swing dramatically day to night temperatures so the fact that it stays within a few degrees makes me think it's just fine. I'll look into a temperature controller. Honestly, if my house did have such swings I wouldn't even have a heater, they make me so nervous in smaller tanks.

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For anybody who would like to use a temperature controller but are deferring due to the prices on some, there is a somewhat cheaper way to get there if you do a bit of DIY.
This is an old post discussing what I used at the time. The new Inkbird models are great but at somewhat higher price.
This is not hard but does take some time and fussing.
http://www.plantedtank.net/forums/9...ing-cheap-digital-temperature-controller.html
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I have the exact same heater with the exact same problem. When I had it in my 5gallon I had to keep it set at 72f to maintain an 80f temperature.
I have the exact same heater with the exact same problem. When I had it in my 5gallon I had to keep it set at 72f to maintain an 80f temperature.
Must be a model thing. It came recommended, and I know that the internal thermometer in those is never accurate. The important part is keeping it stable.

I just put in a new traditional thermometer and I'm getting the same reading as my digital. Been between 81.0 and 81.2 since I've been home this afternoon.
Try and adjust it down... if the temperature rises when the light is on, the thermostat is not the problem, you need more ventilation for the light then.
I definitely need a better light set up, but this is a cappy little kit that is temporary housing for a betta until my aquasoil cycles. After I move him the tank is getting torn down af thrown out or put in storage most likely.

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