Any fully submersible heater will be fine for your spawning tank. Just make sure you run it for at least 24 hours to check that it actually does match the temp on the dial as I've had one in the past rocket off the temp scale when it was supposed to be only at 79!
It has to be submersible as the levels in a spawn tank are quite low at around 5 inches so it needs to go low down near the bottom.