Check the listing for details. Aquaforest Magnesium 4000g in Bucket SAVING TIP!. Condition: New, Made in Poland. Listed at 44.70 USD. A means of increasing magnesium levels in reef aquariums. Magnesium is essential for the proper development of corals. Low magnesium levels can lead to the inability to maintain proper calcium levels and the pH to be too low. The recommended magnesium level in reef aquariums is 1180-1460 mg/l (ppm). Dissolve 10 g in 1000 ml RODI water. The dosage should be determined based on your water test results and the corals' daily consumption. Before adding magnesium solution to the water, you should do a water test to check the current water parameters. 100 ml magnesium solution in 100 l water increases the magnesium level by 1.2 mg/l (ppm). We recommend not increasing magnesium levels by more than 50 ppm daily. KH buffer and reef mineral salt should also be used to maintain ionic balance. Magnesi.