The JBL ProAqua Test Magnesium Freshwater is designed for measuring and doing routine checks of magnesium content in freshwater aquariums within a range of 0-10 mg/l (ppm). + Indicates 0 to 10 as well as > 10 mg/l exactly (recommended value: 5-10 mg/l).+ Very accurate test with 3 reagents.+ The comparator system takes the existing intrinsic colour of the water into account.+ With 2 glass tubes, syringe for the accurate measurement of 5 ml, reagents and laminated colour cards.+ for approx. 60 measurings+ refill pack available Magnesium and calcium together form the total hardness. Like potassium, magnesium is a macroelement which is required for healthy and strong plant growth. The magnesium levels in mains water (including water with a high total hardness) are very often too low for aquatic plants, so that deficiency symptoms appear after a short time already. The symptoms of magnesium deficiency are similar to those of iron deficiency. Yellowing (chlorosis) occurs between the veins o