Difficulties getting cycling tank to 85 F

[teambedell]

I have a Flex 15 new setup that I’m trying to cycle (empty) at 85 F. I’ve read that it will cycle in half the time at this temperature range. I had a Fluval M50 set all the way to 86, but it never got higher than 80 (which was weird because it was turning off/on periodically, as if it was maintaining 80, instead of trying to achieve 86. So I figured I needed a more powerful heater. I replaced it with the M100. It did better, but topped out at only 81.5, set at 86 (still doing the on/off thing). So now I have both heaters in there, at opposite corners of the tank (the M100 is in the sump). We’re climbing again, currently at 82.4. I have 2 thermometers that agree with one another. 
 

Are the Fluval thermostats just plain inaccurate?

Thanks.

[lefty o]

hoooboy! best bet is to run your tank day 1 like it will be with fish in it.  and yes, pretty much all heaters thermostats suck, better yet many heaters will stick on, and youll exceed your 85, and boil your fish. approach things a bit slower please.

[Tony s]

On 3/7/2024 at 9:08 PM, teambedell said:

Are the Fluval thermostats just plain inaccurate

Not as far as I’m aware. I have several working just fine. I don’t really rely on them to accurately read the temperature. Almost all heaters are off in that way. Better is an in tank thermometer used to calibrate the heater. Better than that is a controller with an in tank temp probes used to control the heater. Lucky for you, there is one that does. Unlucky for me, I forget the name. Someone else will fill in the details. The system works really well, especially when keeping dual heaters in the tank. 
 

I’m a bit confused as to why you want to rush the process. I get that it takes a few weeks and sometimes patience is impossible. But the weeks will help to determine what you really want to do with it. 

[Lonkley]

The idea is the bacteria grows faster.

But you're better off with a stable colony at the appropriate temperature.

As for why. It's probably bleeding off more heat than it can maintain

[Tony s]

On 3/7/2024 at 11:48 PM, Lonkley said:

It's probably bleeding off more heat than it can maintain

Possibly. Or undersized somewhat. I was able to get my rams up to 86 using a fluval heater with no problems. No problems but me anyway, I was learning them and ended up failing them.

[jwcarlson]

Don't trust a heater thermostat, that's my advice.  They stink.  I use external InkBird controllers on all of my tanks.

[johnnyxxl]

Do you have a top on the tank, it will lose a ton of heat that way 

[Tony s]

I believe the heater controller I was thinking of is made by inkbird. Something like this 

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwiCuJGV1OSEAxUbGjQIHV9ZDS4QFnoECFIQAQ&url=https%3A%2F%2Fwww.amazon.com%2FInkbird-Temperature-Controller-Thermostat-120V-1200W%2Fdp%2FB07X1JT372&usg=AOvVaw3lVNEberpY3qivd-KmMK8z&opi=89978449

[jwcarlson]

Ebay is the best place to buy InkBird controllers.  I think they have two stores on there InkBird and InkBird USA or something like that.