Thanks in advance. This seems like a good community from what I've been reading so far.
cycle time before introducing the fish:
Freshwater: Depends on the fish. Most of the time as soon as your cycle is over, 1-4 weeks.
Saltwater: Depends on the fish. You cant put a mandarin in anything less than a 6 month tank, some say that is too early due to lack of food. Some say to wait a good 6 months to make sure the bacteria is built up enough. Usually a few weeks though. Salt and fresh generally cycle the same in regaurds to the cycle itself, but the species in FW to SW are different with how they react to it. You have to adjust accordingly. Generally, everything takes much longer with saltwater. Patience is key.
best methods of introducing new fish once some are already in the tank :
FW: float the bag for half hour, release the fish.
SW: drip acclimate for sometimes 3-4hours or longer then quarentine in a quarentine tank for a month, then drip for another 3-4 or more hours and put into your display tank. Not everyone does it, but you asked for the best way. To me, the safest way is best and this is the safest way.
how often to change water[/b]
FW: Depends on how stocked your tank is. Most can take a month or more without changing. Especially with hardier fish. Weekly is best.
SW: Weekly is best with aged, purified saltwater. You have to fill the tank with purified water when it evaporates as the salt in the water will not evaporate and will cause the salinity of the water to rise.
In general, everything is much more expensive and takes alot longet to sey up. Especially if you go with a reef rather than fish only tank. For a reef, you need $400+ in lights alone usually depending on the size of the tank. Bigger is better here, as it will be easier to keep the water parameters in check with more water. You will need a protein skimmer running hundreds, LR running hundreds, and live sand (or aragonite or crushed coral) which could also be expensive. All this is before corals, inverts and fish. There are many routes to take. If you do a fish only tank, you dont need much lights at all, and you only need sand and rock, none of which have to be live. No protein skimmer necessary, a canister filter will do.
I dont mean to try and scare you away here as it is an amazing practice. If you get into saltwater, be prepared to do TONS of research and wait a long time before you do anything with that tank. Always keep the fish's best interest in mind and dont cut corners. You will be kicking yourself in the long run if you do. I suggest you read "The Conscientious Marine Aquarist" by Robert Fenner and read TONS on this board before making any decisions. I, and many others will be here to answer any questions you have. Good luck with whatever you choose.
Mark