Depends on several factors, how good is your filter system, how large are your neons (small or full grown), do you tend to overfeed your fish, etc. The old rule of thumb was 1 inch of fish per gallon of water, but I've always gone much higher than that, doing more frequent water changes and watching how much they are fed so there isn't much extra food floating around or lying on the bottom after feeding. So in theory, if there was no filter system, one fish per inch = 40 neons. With a filter you could go higher, but allow for fish habitat, which reduces available water volume: gravel, rocks, etc.
The fish bowl must be at least 1 gallon. You can fit 3-5 tetras in there. However, if you put them in a fish tank with a filter, they will live longer and will be healthier.
You should only have 1 fish per gallon of water in a fish tank. I wouldn't put more than 2 or 3 Neon Tetras in a 4 gallon aquarium with 1 Betta.
You would probably be fine with 5-10 neon tetras.
many small fish such as small tetras, rasboras, smaller shrimp, guppies, platies, endlers, etc. or, you could get a betta with a small school of tetras as long as neither of them are fin nippers as their personalities vary by individual.... (the betta would love you for all the room)
NONE Oscars are really messy and grow up to a foot! They need at least 50 gallons. For a 10 gallon I recommend some guppies and neon tetras.
a good rule of thumb for stocking aquariums is one gallon for every inch of fish.
Neon tetras should be kept in a school of at least six individuals for optimal health and well-being.
I have about 12 in a 70 litre tank and they seem very happy together
Bettas are generally kept in their own private tank, since they can be quite vicious to other fish.
There are many species that come from the same areas of the Amazon river and its tributaries. Most of the Tetras including Cardinals are OK with Angels. Please remember that Angels grow into quite large fish and 2 Adults would need at least a 30 gallon tank.
This is not a smart idea because only a one gallon tank is very very small! For future advice a very safe way to determine how many fish to put in a tank is to have about an inch of fish for every gallon. That applies to small fish. Larger fish need more room, and goldfish need even more room (20 gallons per fish). This is to make sure they have enough space to grow and live their entire life span. A 1 gallon tank is difficult to heat properly, and tetras are tropical so they need warmth.
1000