How tight do you need the range to be?
Is it for a one off breeding project or is it long term?
Most aquarium heaters don't specify a range so you are likely to get a fluctuation of a couple of degrees e.g. set the temp to 88
temp is 84 so the heater comes on
temp reaches 88 and the heater turns off
Heater does not come back on until the temp drops to 85
Conversely I have a really cheap heater with a very narrow range. I find it annoying in a fish tank because it regularly turns itself on and off every few minutes - so I suspect it won't last very long. I keep this one as a spare and don't usually use it. Oh and the calibration is way off. It does maintain a constant temp - but its about 4C (8F) different to what the digital display reads
You would be advised to calibrate the temp anyway as these can be some way off (even with the more expensive heaters).
I am not sure what the objection is to thermostatic controllers but I have found the Inkbird ones very reliable and accurate (and inexpensive). I use these in all of my fish tanks and can set the on and off tempratures separately with an accuracy of 0.1C. I have never checked the F settings because I can't get my head around farenheit
. All 3 of mine were 100% accurately calibrated out of the box, but if needed you can calibrate the display to avoid giving yourself needless stress when you do a temp check half asleep and it shows the wrong temp