Hi and welcome to the forum
What are the tank dimensions (length x width x height)?
What is the GH (general hardness), KH (carbonate hardness) and pH of your water supply?
This information can usually be obtained from your water supply company's website or by telephoning them. If they can't help you, take a glass full of tap water to the local pet shop and get them to test it for you. Write the results down (in numbers) when they do the tests. And ask them what the results are in (eg: ppm, dGH, or something else).
Depending on what the GH of your water is, will determine what fish you should keep.
Angelfish, most tetras, barbs, Bettas, gouramis, rasbora, Corydoras and small species of suckermouth catfish all occur in soft water (GH below 150ppm) and a pH below 7.0.
Livebearers (guppies, platies, swordtails, mollies), rainbowfish and goldfish occur in medium hard water with a GH around 200-250ppm and a pH above 7.0.
If you have very hard water (GH above 300ppm) then look at African Rift Lake cichlids, or use distilled or reverse osmosis water to reduce the GH and keep fishes from softer water.
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Neon tetras should be kept in groups of 10 or more.
Cherry barbs should be kept in larger groups 6-10 or more.
Corydoras should be kept in groups of at least 6 (preferably 10) or more.
Rainbowfish should be kept in groups of at least 6 (preferably 10) or more. Most rainbowfish need a tank that is at least 3 foot long.
Never keep more than 1 species of cichlid per tank. Blue rams and Bolivian rams will fight. Bolivians need a tank that is at least 30 inches long. Blue rams should have a 30 inch+ tank too but you might get away with 1 or a pr (1 male & 1 female) in a 2ft tank.
Do not buy balloon fish of any sort. They have numerous health issues, can't swim properly and usually die prematurely.
