Eheim jager taking awhile?

[Hybridfish7]

I'm assuming the temperature of the room drops below 70F at night. The heater you have right now is rated for exactly a 52g, so either the heater is not working properly or it is constantly fighting the night temperature drops, hence the reason for it taking so long to heat the tank and keep it there. Most heaters are rated for a 10-15 degree room temperature vs tank temperature difference. Once you go beyond that swing, you need a larger heater or a second heater.

I would get a second heater for the tank.

Ah I see, gotcha. Also the tank is a 40B

 

[Hybridfish7]

Update, finally got the tank up to 87. New heater does appear to be working.

 

[TwoHedWlf]

so after 14 hours of having the new one in and set to 87, I got it to 84. Is the heater just too small? I thought the 125 was for 50 gallons.

Ratings are basically useless, they're for consistently warm rooms and heating tanks not much above ambient, and then they throw in a marketing fudge factor.

I made some estimates of dimensions and plugged them into a heat loss calculator here: https://www.hamzasreef.com/Contents/Calculators/HeaterChillerSizing.php

It calculates your heat loss as 200 watts at 86°F. You'll never get it to 86 with only 125 watts. You have your actual measurements though, so you can probably get closer calculations.