if you plan on having 5 adults and 10 juvis/babies. $7(for thermometer) x 10(tubs)= $70 with out tax.
temp gun $20-$50 and 1000X times easier than dealing with thermometers.
the hydro is a thermostat not a thermometer. The hydro will tell you what temp you have the heat set at but not how hot it is inside the tubs. example i have my herpstat set at 94.5 degrees for my rack, on the hot side of the cage it is only 90-91 degrees. the temp gun will tell you hot hot inside the cage is the hydro will tell you how hot you have the heat set to.
think of it as you thermostat(hydro) in your house, is set to 70 degrees, it doesnt mean that every room is 70 degrees.