Well depending on how dense the rock is you will need about 1-1 1/2 pounds per gallon, I think DSB's (deep sand beds) are the way to go so on a 55 you should have between 70-90 lbs and I would just get dry argonite sand as it is much cheaper and your LR (live rock) will seed the sand and make it live. I think refugiums are the way to go for filtration and a 29 gallon would be good for a 55, here is a link for sumps, refugiums http://www.melevsreef.com/allmysumps.html . You are going to need PH's (power heads) and I would recomend 2 Koralia 3's and I suggest a good skimmer, I like the ASM's Euro Reef's and the Octopus skimmers and you ashould get one that is rated twice the total water volume of you system as they are usually over rated some. With lighting if you plan to keep clams or anemones you will need intense lighting as in upper end T-5's or MH's, the T-5's dont produce as much heat and are usually cheaper to run and bulb replacement but you wont get the shimmer lines, the MH's do produce a nice shimmer line and alot of people like that. I would suggest looking at as many tanks with different lighting in person as you can to get an idea what looks good to you. I am not trying to confuse you but this hobby can be confusing and it is better to know the different posabilties before you buy any htimg so it will be cheaper when you are finished with all the purchases. Have fun setting it up and watching it grow and keep asking questions :grinyes:.