My betta recently passed from cotton mouth. How do I disinfect the heater that was in there? It is a normal adjustable Aqueon heater. Can I use vinegar? I don't want to use a heavy chemical like bleach.
We need more information. Is the heater currently in use for any other fish or was it just used for one Betta? If the heater is not in use for any other fish and you don't have any other fish in the tank MEANING the tank is completely EMPTY except for decorations AND NOT A PLANTED TANK you can treat everything with salt (Canning/Pickling Salt or Aquarium Salt, Your choice). IF THE TANK IS EMPTY OF FISH AND/OR LIVE PLANTS, I would treat with salt and turn the heater up to 88-90 Degrees and leave it there for 10-14 Days. You Could also get some Aquarisol and do the same thing. Turn off your filter for 10-14 days, if you have a filter and just leave the tank alone.
I am telling you the way I would treat it if it were my tank..And Yes, you would have to recycle the tank. Salt works great if you are not in a hurry and it sounds as if you are. You might want to take a look at Aquarisol. I don't like using anything other than Salt or Aquarisol. Sorry, I have found that having patience often proves to be a better solution as opposed to using and introducing the possibility of any "fast" method.
Trust me, from where I sit and type I am not trying to be argumentative with you I am just trying to understand why you would want to just clean a heater and not your entire tank since your fish was using the entire tank.