i showed this idea befor and i rethought it and im gonna try again. the 55 is established about 10 months old. the 30 gallon will only have crushed coral bed about 2 to 3 inches. when i start the pump it will be just like doing a 60% water change. can someone experienced tell me why or why not this will work. i know someone who has done it and they say no problem. the only thing that bothers me about it is the bacteria. could i use something like "cycle" at the start? and will this scenario trigger a cycle with ammonia and the works. basically turning a 55 into a 90 gal. system. i have a skimmer good for 100 gallons. please send feedback. thanks. raymond