Gravel bedded tanks have small distributor baskets at the bottom, surrounded by gravel and can slow down your flow rate. With a Vortech plate in the bottom of your tank, it covers the entire diameter of the tank, has slits cut throughout the plate, water comes in through the upflow inlet, flows down through the center distributor tube, and up through the Vortech plate in a circular motion.
Vortech tanks eliminate the problems of gravel bedded tanks like channeling or calcification of the filter media. They also give you much better flow rates than gravel bedded tanks.