the heater is 300w in the vertical position midway between the intake and spray bar on the back wall, the tank is 75 gallons standard, the thermometer is on the front wall left corner about 20 inches opposite the intake and 24" diagonal from the heater, im using a sunsun (dont laugh) canister filter rated for 80 gallons the intake is on the back wall in the left corner, the spray bar is attached to the right wall facing intake opposite, pissing at a 30 degree angle about an inch above the water to promote a decent deep current without submerging...

now, i originally set the heater to 77, thermometer reads 73, so i cranked the heater up to about 80 and i havent noticed a change in temp on the thermometer yet, could be too soon, been about 3 hours, when the heater was set lower it seemed like the light came on sort of often in retrospect, but not enough to make me suspicious, and not nearly as much as it does now. its on for ten seconds off for ten seconds, roughly. much more briefly than my other heaters, i had a heater rated for 15 gallons in this 75 gallon that didnt seem to work nearly as hard (or get my water past 73), and this was supposed to be an upgrade. i dont understand it, it seems like the thermostat knows that the right temperature has not been achieved, so it cuts on, but then only a few seconds later it thinks it did the job and cuts back off. i know they cut on and off as they reach temp and the temp drops ad nauseum, but intervals of only a five to ten seconds? i have a 200w heater in a 20 gallon tank with a filter rated for 30 gallons, and its working wonderfully, same brand, technic i believe.

ten bucks for a 300w heater, so i wont be utterly heartbroken, but i was wondering does anyone here have any experience similar to this? should i replace the heater? does it sound like its going to fry my tank or burn my house down? with larger heaters and tanks is this just normal? is my electric bill about to skyrocket? i hope i posted in the right spot, good bad and ugly input is welcome, t'anks (check out that pun!!!) in advance!