No it is not need, but it is one of the trace elements that a Ca reactor can not give you. I test bi-weekly and keep the levels at 0.06
I dose it for my shrimp and clams
Here is the dosage instructions:
Determine the iodine concentration in the aquarium using an accurate test kit before supplementing. Each ml of Brightwell Aquatics Lugol’s will increase the concentration of iodine (“”) in 1 US-gallon (3.785 L) of water by 34 ppm, or approximately 1.7 ppm per drop. Add this product at the maximum dosage of 1 drop (1/20th ml) per 35 US-gallons daily to maintain a concentration of 0.05 ppm. Always try to maintain the within a range of +/-0.02 ppm. Determine the required daily dosing rate (recommended to weekly dosing) by measuring the aquarium's at the same time each day over a one- to two-week period. Estimate the volume of water in the entire aquarium system; divide the daily decrease in by 1.7; multiply this number by the volume of water in the system to get the daily dosage required (drops) to maintain a stable .