yeah that's what i calibrated ro/di to... just saying that the difference of measurement is .002 between each of these.... The difference quite big with Pinpoint fluid and RO/DI at .004... With aquacraft it's only .002 difference... not sure which one is most accurate but Tom Blevins uses RO/DI and his tank looks fantastic... Makes me worry that if you're going with Pinpoint, your tank may be too salty...