Cold holding is an integral part of food safety.
Holding food at incorrect temperatures is one on the top 5 reasons there was an outbreak in this county.
Depending on your jurisdiction you may not be required to log the temperature more than once or twice a day and often there are no requirements for logging. I recommend that you check and log refrigeration equipment temperatures every 2 hours to ensure time to take a corrective action. The inside thermometer is sufficient for logging however, you need to ensure the thermometer is accurate. I recommend checking the internal temperature of a sampling of food at least once a week and comparing with the internal thermometer. You should also do internal sampling anytime a thermometer is dropped to ensure proper calibration.
Verification through logging
Have staff record the internal temperature of all equipment in a daily log book and a shift manager should review recordings for possible problems. In my experience, as a third-party inspector, I often see log books that are completed with temperatures outside the critical limit with no action being taken. This has cost business big money when all TCS foods must be discarded.
If you find that food is stored above 41° F and the time is less than 4 hours and verifiable, you can move the food to a freezer or walk-in for quick chilling. You must check the temperature before the end of 4 hours to ensure the food has been returned to 41°F or below. If it is still above 41°F you must discard.
Staff should be properly trained on how to take internal food temperatures and the proper location the hanging thermometer should be placed in the unit. Hanging thermometers should be placed in the warmest part of the unit, which is usually just below mid-point on the and toward the front where the door opens. When taking internal temperatures use a thermometer that has been calibrated. Do not touch pan sides or bottom.
FDA food code 3-501.16(A)(2) and COMAR 10.15.03.06 b(7) states that cold food be held at 41°F or below.
In Maryland, you must store pasteurized crab meat at 38°F or below.
Always check with your local jurisdiction as recommendations / requirements may be different.