Temperature fluctuating like crazy

[Bhopkins1311]

So I got my 55 gallon tank used. It came with 1 100 watt submersible heater on a pre set temp? (idk what preset temp is) and then I got 2 long unbranded ones (I posted pics) one is 100w and the is 200w. Those have a nob but no dials to see what I'm setting temp to. So black submersible usually keeps it at 70 to 72... I came home one day and temp was like 60 so I put in other one and then came home and it was at like 81 so took that one out and just had black one and it only went down to 78 I just have zebra danios and I want the temp about 75 because that will be the temp when I add more fish

 

[Aquaphobia]

I don't see the picture but all you can do is turn the dial counterclockwise a little at a time and leave it each time for a while and check your temperature.

 

[Bhopkins1311]

Here are pics

 

[Aquaphobia]

I would say that 100w isn't strong enough to maintain temperature in a 55. The presets I've known have all been set to 78. Maybe 2 of them together would work but I would go for the 200.

 

[Bhopkins1311]

I have 1 submerseable one 100w

The one in pic which is 100w
And a 200w same kind as one in pic

 

[jickey]

I run a 300w in my 60 gallon and it holds 76 easily. Honestly, since you don't know how old those heaters are and they don't have a good way to tell what your temp setting is, you should probably just pick up a new one (or two.) Go 200w minimum. They're cheap and you can have more peace of mind with them. Eheim makes a Jager 300w for 30 bucks on Amazon. One thing to think about - sometimes when a heater malfunctions it breaks in the "on" position (the thermostat goes out.) This typically leads to a really expensive fish stew

 

[Bhopkins1311]

Oh jeez yea imma get new heater I don't wanna fry my fish

 

[aliray]

I had that happen twice on the 10 gal tanks with the heaters that came preset in the kits. Didn't loose all my fish but did loose some each time. Got 3 all new adjustable heaters So far so good. Alison

 

[Bhopkins1311]

What kind of heater did you get

 

[jickey]

look at the Eheim Jager - I believe it has a ring that you can use to calibrate your heater once you get it to temp. Eheim is quality stuff too.