
The rule of thumb for stocking fish is 1" of expected adult fish size per gallon of tank. 10 gallons is a very small tank, and it is never a good idea to fully stock that small of a tank.
I will address the fish question later, first I must ask about your tank. How long has it been set up? Do you test your water for ammonia, nitrites and nitrates? You said in your aquarium information that you don't know about the nitrogen cycle.
Basically fish waste and left over food produce ammonia, which is toxic to fish....bacteria has to develop in the tank that will convert ammonia to nitrite, that is also toxic to fish, but once nitrite have started to develop, another bacteria establishes itself that will convert the nitrite to nitrate... Fish can live and be healthy in a tank with nitrate levels up to 20. Any time there is any reading over 0 on ammonia or nitrite you have to do a 25% water change every day until the cycle is finished.
Now to completely explain the nitrogen cycle to you , go to the link at the top of this page under "ARTICLES", click on Nitrogen Cycle and it will tell you all about it.
The worst thing any one can do to fish is place them in an uncycled tank. Within a week they will start getting sick, and without water changes most will die of new tank syndrome (an uncycled tank).....
OK now about the stocking.
Your aquarium info says you have 2 mollys...they are counted at between 3 & 4 inches each. So you could have the two mollys, but you should then take the rest back, because the mollys, unless they are both male, will have fry.
IF you took the mollys back you could keep all three platties, but no more, because once again, they will have fry.
If you take the mollys and platties back you could get 3 more cardinals and just keep the neons and cardinals, 6 would be the minimum for these as they are schooling fish, and that would be a nice little school and 6 would fully stock a 10 gallon tank. Problem here is that these would not be the best choice in an uncycled tank, they are fragile and may die.
Your choice, this is just the best advice I can give. Good Luck.
