Red Sea Plant Lab Aquarium Test Kit. **** PRODUCT MANUAL **** Red Sea Plant Lab measures: CO2 & Iron. These are 2 Essential Tests for Planted Aquariums. Carbon dioxide is the most important plant nutrient and is sufficiently and constantly supplied in natural waters by nutrition springs. These natural sources of CO2 are missing in the aquarium and it is, therefore, prudent to check the CO2 contents regularly. A consistent CO2 level of 30-40 mg per litre is necessary for a healthy growth of all aquarium plants and at the same time absolutely safe - even beneficial - for the fish. Plant Lab Test Kit - Includes 60 CO2 Tests and 60 Iron Tests.