Hi...I have a 29 gal (not used) and a 55 gal. I switched from CC to Live sand for my 55 gal and live rock. When I had the 29 gal. I had to chg water every 2 weeks...Now I have the 55 gal with live sand and live rock, clean up crew, plus Fluval 204 & 304 filters,,,,the water is beautiful. I...