Agree with everything M3ace9 said. The main cons are price, upkeep, and ULNS (ultra low nutrient system) and all it entails. UNLS is not a con per se but softies and LPS will generally not thrive in that type of environment without regular feeding and careful dosing and nutrient management. Are you going to go full blown SPS dominated? If yes, then Zeo could be good if you don't mind the high costs and frequent dosing, agitating zeolite media etc. If you're doing a mixed reef then you may consider doing a zeo hybrid or just cherry picking a couple zeo products to use in conjunction with Bio-pellets.