You should not use cedar unless it is very well seasoned. Since cedar is aromatic, it gives off resins and some have reported problems. Others had no problems with well aged piece. You use cedar at your own risk!
Other woods to avoid - any pine with pith, <actually most people just say avoid all softwood altogether,> any poisonous species (like black walnut).
80 gal FW with 30 gal DIY wet/dry/sump.
9 fancy golds, 1 hillstream loaches, 1 rubber-lip pleco (C. thomasi), 3 SAEs, small school of white cloud minnows, planted.