That is a nice big tank to start out with. We do need to know whether the tank is 250 or 300 litres. Most people on this site are American, so to ease the onfusion 250 liters is around 54 gallons, and 300 liters is around 79 gallons. I may be wrong, though. For my stocking suggestions I will pretend you have the 54 gallon. You can do a ton of stuff in a tank that large. Your big desicion is basically whether you want several large fish (ie. 4 fancy goldfish like these: http://www.tropicalfishkeeping.com/profiles/goldfish/
, stay around 8-10 inches, don't go for the goldfish that most keep in bowls, as they grow upwards of a foot long), or many little schooling fish, such as tetras, rasboras, corydoras catfish, platies, guppies, and mollies. There are many different species of tetras rasboras, and cories, so make sure you get all of the same species. If you don't won't have others to school with which makes them stressed out, and die. Stocking also depends on your area's water quality, some species prefer hard water, and others prefer soft. Goldfish and livebearers such as guppies platies and mollies need hard water to thrive. Most tetras on the other hand prefer soft. There are other species like corydoras catfish, and bettas who don't really care.
Some hard water set ups for beginners:
54 gallon Fancy Goldfish Tank. This is a harder choice than the other set up as Goldfish require multiple filters, need to be cleaned a lot, and prefer special home-made food. But, goldfish are very social fish and are absolutely adorable. They come in many different forms, but it is best to stay away from bubble eyes, as they need special care that is too hard for beginners. It's basically your preference. They also need heaters for a steady temperature. If you decide on this talk to some members that keep them like Olympia who has a 90 gallon goldifsh tank, and thekoimaiden who has a 55 gallon and has kept them for years.
-4 of any type
54 gallon Tropical Community Tank. This is easier, and completely different choice than the goldie tank. These guys are all small schooling fish, that are in groups of 6 or more. They may not have as much personality as the goldies, but don't require as much care. They only need one filter, cleaning once a week, and a heater.
- 8 male platies (don't mix males and females as they breed like rabbits, i learned this the hard way by getting all females who were all pregnant from the store) http://www.tropicalfishkeeping.com/profiles/platy/
-8 red-eye tetras (don't have these if your water is like liquid rock) http://www.tropicalfishkeeping.com/p...red-eye-tetra/
-8 x-ray tetra
-8 pepper corydoras catfish (again, not if your water is more than moderately hard) http://www.tropicalfishkeeping.com/p...s/pepper-cory/
The platies will swim at the top of the aquarium, tetras in the middle, and cories at the bottom. If you want cories you need to use sand not gravel as their barbels can be damaged by the gravel
Soft Water Setups:
54 Gallon Tropical Community Tank: Same basic care as other tropical community tank.
-8 silver hatchetfish (can and will jump, so make sure your tank has a lid and that you are careful during cleaning)
-1 male honey gourami (very pretty centerpeice fish, they make little nests full of bubbles like betta fish)
-12 rummynose tetra
-12 ember tetra
-12 pygmy corydoras catfish (reguires sand instead of gravel like all other cory species)
hatchets will swim in the top, gourami all over, tetra in the middle, and cories on the bottom
Make sure that you get a good quality hang on the back or internal filter like these: http://www.petsmart.com/product/inde...AvailInCA%2FNo
And that you have a good heaater that keeps the temperature steadily warm. The general rule is 5-10 watts of power per gallon of water.
If you need to learn how to clean, let me know and I can help with that too. I hope this made any sense at all. haha