really not much to it over fresh water.
get a hydrometer. later a refractometer. these measure salinity (saltiness) of your water. you dont want your water to be the red sea right?
get a heater and start at 78 f. anything below 72-74 and anything above 86 you will run in to issues.
remember that hydrometer? well it's measurement will be off of the temp of the water and is different than what the factory calibrated it at. (usually 60f).
target 1.022-1.023 on your hydrometer. if you went refractometer you will have to make sure it is calibrated and can disregard.
so we have water at 78 f and hydrometer reads 1.022-1.023 (if instant ocean) but really you are at 1.025. this gives us a little breathing room for evaporation.
as your tank does it's thing it will slowly evaporate h2o. but the salt will stay in there. so more salt per h2o due to evap gives us a little wiggle room. we dont want salinity (saltiness) to go above 1.027. or probably 1.025-1.026 on the hydrometer. all we do is add pure water (no salt) and we are back to normal again.
k so we have water and temp. woot! lets look at filtration. a good baseline for filtration is 1-2lbs of liverock per gallon. hang on back filters arent going to cut it with our lil piece of the ocean. we need to use rock. in this rock, it will house all the fun stuff to eat all the waste fish give off. you dont want them swimming and breathing their own pee and poo do you?
so if i have a 20 gallon tank, i would need roughly 20-40 lbs of nice porous live rock. porous being that it has caves and holes and lots of dimples. you dont want to use marble or granite. just nice textured, and holey rock.
sand can be of whatever choosing. avoid crushed coral. it traps waste from fish that the rock can never get at to break it down. sand is preferred. 1-2 inches. later when you get the hang of things... you can utilize other strategies. but for now no more than 2 inches.
now we need some sort of flow. flow is what transports nutrients around so that other life can grab it. it also allows gas exchange so that fish can breath. you dont want a puddle of bleh that kills your fish so we aim this at the surface of the tank so that gas exchange can occur. you want nice little ripples on the top of the tank's water. by doing this you introduce oxygen so fish can breath while getting rid of co2. (in laymens terms)
now to cycle.
there are many many manyyyyy ways to cycle and i will not go in to it on this post. however, you will have the beginnings of a basic saltwater tank.
lighting
another subject. what donyou want to keep? stick with zoas for your first coral. or even a duncan. these are pretty hearty corals and arent a nuisance weed like xenia or kenya trees or green star polyps.
get a basic marine test kit!
you need to know your ammonia, nitrite during the cycle.
nitrate always
phosphate kit always
want corals?
magnesium, alkalinity, calcium kits will do you well.
most importantly have fun. and realize, you can make this as complicated as you want. i think these first few steps will help you with the next one
hth
