There's really no need to change out bio-media, unless it is falling apart or something. Could cause a mini-cycle, especially if you change the sponge as well.
29 gallon, Fluval 306. Aquatop PF25-UV Power Filter, 1x39 watt T5HO 7" above tank. P.F. Sand, Pressurized CO2, 5 Glowlight Tetra's, 3 Halequin Rasborah's, 3 neons, 2 Oto's, 5 Cherry Shrimp, 4 Amano Shrimp.