sticking thermostats on heaters

[ironbone]

all my water heaters are being difficult for me,work fine keep temp for awhile than they start sticking and staying on adjust works fine for while than again adjust ..well you get the picture
so they are on the lowest setting and still they stick?i used the 50watts per 10g,and moved down
in wattage and they are all doing same thing.there not cheapies but there not top of the line is there something i can do to keep them from sticking?

[Pufferpunk]

What brand are your heaters? Are they the correct wattage for the tanks?

[ironbone]

3 are thermals?1 is aqurium products came with set up.puffs heater i believe i broke the dial that explains why it just bit it.the others didnt have problems with so i stuck with them.now they all bite the dust,well be difficultcmon
on my wc today lost 2 degrees waited 15mins plugged in it was on every since,maybe im freaking temp went to 82 on my mollie tank i dont want to ruisk that on puffs
tank.i found with the mollies they are more forgiving on temp change,but still if heater is sucking.why does it go wacko for a day than back to norm.uggghhh.puffs been 78 forever to drop 4 degrees sucks i think thats why i was tripping over heaters.i guess ill go shopping for a better one any ideas and dont bombard me me please .full marine heater?i stepped up into sw so things get a little pricey thats fine im gonna try aqeon filter pp says they rock so ill try little pricey but if puffs happy worth it

[Nick]

Some heaters do temperature regulation with a thermostat in the heater, while others have a "duty cycle" where the amount of on time and off time is loosely controlled by the dial. The duty cycle type vary MUCH more with the room temperature, heat from lights, etc.