Why is finding the increase in fresh mass not reliable?

Finding the increase in fresh mass can be unreliable due to variability in water content, which can fluctuate significantly based on environmental conditions, handling, and timing of measurements. Fresh mass can also be affected by factors such as dehydration or moisture absorption, leading to inconsistent results that don't accurately reflect the actual growth or biomass increase of the organism. Additionally, fresh mass does not account for the dry mass, which provides a more stable measure of biomass that is less influenced by these external factors.