What is the tank temp run? I have shrimp tanks with not heaters at all running.
My thermometer states around 80. I know it's off 3-4 degrees (on the high side).
As mentioned, your best option is probably no heater for most shrimp.
I ended up disconnecting the heater and have had no deaths. Right now its in between 70-80.
I purchased an infrared thermometer today so once I get the battery put in, I should have a better reading of the shrimp tank and my 30g.