good question yeah but its not accurate enough to give you pinpoint accuracy..so..for your fishes sake I might stick to a tank thermometer...but if spot on accuracy is not necessary...by all means it will give you a decent reading
Sometimes it’s called a laser thermometer, because you use the built-in laser to target the surface, but it’s really a non-contact infrared thermometer that measures the electromagnetic radiation coming from that surface. It’s the safest way to measure temperatures in hazardous areas (like automobile engines or other machinery), hard-to-reach places and other areas where a non-contact infrared laser thermometer is the way to go. Professional-quality, infrared technology at an excellent value Temperature range: -4° F/-20° C to 968° F/520° C Accuracy: +3° F/+2° C or 2% of reading Distance-to-spot ratio: 8 to 1
http://www.harborfreight.com/infrared-thermometer-with-laser-targeting-non-contact-69465.html - this is the item here on harbor freight web!
it shows a computer being read on the front of the package, Def inside we used it to check heat escape from roofs in winter...worked fine outside giving a good heat reading of escaping heat...like the description says its....pretty accurate...however we needed one that read moisture content and was pinpoint like if I point it at my mouth open it reads a touch low however I have never used a human thermometer to check it against....so....thats the best I can do hope that helps