well i usually clean my res-a-craptor around every 2 months but thats just me like i disasemble the blocks and scrub them with a toothbrush.u should change the fluid every 6 months at least. i did some experiminting and i founs that distiled water mixed with water wetter gave me the best results ( water wetter increases the amount of heat the water is able to obsorb). remember you can clean all your blocks in normal tap water but before you asemble them you MUST rinse them in distiled water so they dont get little goopy stuff growing on them.