Botanicare OD Tray 4 ft x 8 ft Black Water Pumps Aeration & Irrigation targeted to encourage excellence from HGC708220 1 targeted to encourage excellence from your plants Calcium (Ca) and Magnesium (Mg) alleviate the potential elemental problems commonly seen in this unique growing media because they powerfully deliver these critically essential secondary and micronutrients to your valuable plants at the most crucial time so you get the optimized yields you desire These trays sit in the precise footprint that their name suggests and fit easily into all growing tents on the market these new OD trays are an economical purchase for the space minded consumer