There are many fish that you can buy, and some are good fish, while others are horrible to othes, and still some are just plain rude. Of these fish, only a few are a good fish to start in your tank, but these are usually cheap.
Here is a quick list of some good fish for you to get started in the bobby
All of the fish in that list are good beginner fish as they are cheap, hardy, peaceful, and will accept a wide range of food that is offered to them.
Some people say that the best starter fish are damsels or chromis. This is not true, as damselfish often create huge territories where ither fish cannot enter, and will fight other fish, maybe even causing them to die. They are also pretty picky eaters, and don't usually swin to the top of the tank where the food is.
However, most people will say that blue or green chromis are the best beginner fish. This is true to some extent. While it is true that they are very hardy, they don't really do well if there isn't enough of them in a tank, as they are schooling fish, and there isn't enough space for them to hide. They are also known jumpers, and they will often vanish from the tank without a trace. Not a sindle bone or fin anywher in the tank of surrounding floor.
It is recommended to put one inch of fish per 2-3 gallons of tank wayer, and that is the fill grown size, not juvinile size. Also do not double your fish cound in a month, so start with one fish, another the month after, and possible 2 the month after that. Because of this rule, I wouldnt recommend add a clownfish as your first fish, as it may get territorial and won't form a pair when another is added the month after. I would start with something like a firefish or a goby, blennie, or dottyback.
Now for basic care. Before you even add your fish, make sire your rank is properly cycled, and that the salinity is at or near 1.025 specific gravity. you can check what this is by using a measuring tool like a hydrometer.
Now its time to acclimate your fish. You can do this by either float acclimating or drip acclmiating it. Fish are generally less sensitive than fish, to float acclimation should be ok. Clip it to the side of the tank with the bag open, so it can get some air, and the bag won't float aound. Let it sit there in the water until the tempurature of the water in the bag is the same as outside the bag. Now start slowly doubling the amound of water in the bag with water from the tank. Do this over the course of about an hour. Then take half of the water out of the bag, and repeat. DO NOT put the store water into your own tank. you do not know what parasites or bugs are in there. After you are done acclimating, use a net or your hand to scoop the fish out of the bag and into your tank. Again, try your best to not get water from the store into your tank. The fih should be fine while doing this, as it can survive a minute or two out of the water.
Now observe your fish for a few days with the lights off, to make sure that the water is clean enough to sustain a fish. After a few days or so, you can turn the tank lights on.
After a month, it is time to add your second fish. Repeat the same process, but you dont have to turn off the lights while doing this. Each time you add fish, try to determine how bog it will get, so you can know if you are able to fit more fish in the future.
Now on how to actually care for a fish. They need food. Fish are generally small and so are their stomacks, so they only need a small pellet or two for inch of fish. Also, if you overfeed the tank, it will cause algae problems from the uneaten food, and the food will bloat in the fishs' stomach, which may cauze it to die. Fish don't know this, so it is up to you to manage their feeding.
Most of these fish are pretty hardy, and can withtand wter that is not the best, but try to keep your water good qualitu for your fish. You can do this by testing the chemicals in the water using test kits, and lower or raise certain chemicals by dosing, using other chemicals that can neutralize toxis, or by doing water changes. (try to do water chages at least once a month.)
If you have a protein skimmer of GFO reactor, make sire you take care of them. Clean the skimmer cup when its dirst, and change the stuff in the GFO reactor at least every few months. Also be sure to change the filter socka fi you have them, and remove some of the algae in the refugium every now and then, removing nutrients from your sytem.
Many fish also have specific care requirements that you need to adress if you are considering getting one. Line gobies need a sandbed to hide in and for them to find food in. Tangs need rocks and algae that can grow on the rocks, as algae is their main diet.
Again, before adding more fish, make sure that you have enough space for it. If a fish gets too bg, you can also return or trade or sell it to a local fish store. Also, before adding more fish, do your research. Make sure that your new fish won't fight other fish and won't eat corals. If any of these traits are present in your new fish, either don't buy it or make sure you can limit the fighting with enough space for the other fish to hide or run aawya from the bully fish.
Also don't get predatury fish like engineer gobies. Though they may be pretty and easy to care for, you don't want them eating your other fish.
You may want to invest in a powerhead. This is because many fish come from parts of the reef that have a lot of flow, and will apreciate that. Flow also helps to clean the fishs' hiding sopts, and it mayhelp then get some excercise or something to do instead of floating around by riding the flow.