Submersible water heaters

Sounds like you want a cup boiler or travel immersion heater. Something like one of these on Ebay.

Not a recommendation but I think this is one of the cheapest:

Somewhat less-disreputable ones are available eg

These ***don't*** have thermostats.

Owain

I have seen metion elsewhere of ones just like the aquarium ones, but for up to about 50°C to 55°C for PCB bubble etch tanks.

I have also seen a website showing how to construct such a tank showing that an aquarium type can have the thermostat knob stops removed, allowing it to be turned up higher.

Only what I have read though.

SteveW

I use a pair of aquarium heaters that I use for keeping a nickel plating bath warm. I was dubious about their insulation initially but in practice they have been fine totally imersed,

Andrew

snipped-for-privacy@gowanhill.com explained :

Two pin (no earth), now if that element metal jacket were to accidently become live...

If you want something reliable then Radiospares (or whatever they call themselves now) do a reasonable range. I've never looked for thermostats, but I'm sure they exist.

Web page helpful:

"Don't put your hand into the liquid when the element is plugged in a wall outlet."

Kindly to read all instruction as manufacture most anxious not kill esteemed purchaser, you always happy.

Owain

Depending on the application a method of stirring water also may be required.

snipped-for-privacy@gowanhill.com pretended :

Oh, that is fine then lol

I'd buy an immersion heater flange to install into the tank and go for a bog standard immersion heater with thermostat. Very simple and freely available.