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How much...it really depends. I can not give you a number. I will offer that it is expensive and there tend to be some unaccounted for costs. That said, with careful planning you can do it without breaking the bank. Try starting with a mix of live and base rock. The live will seed the base rock and it will all become live over time. Start with a good quality aragonite based play sand for substrate instead of "live sand" from the LFS
. It may take a bit longer to cycle using this method but you can use the time to save up for the extras like powerheads, test kits, etc... Remember that start up is the biggest expense of a tank so if you go slow it will not be as hard on the pocket book. Remember that nothing good happens fast in this hobby anyways.