If by "comet fish" you mean a comet goldfish, you should not put anything in with it unless you get a much larger tank. A comet goldfish can grow six inches or longer, and will need a larger tank. Any tankmates should be cold water fish, like the goldfish. Snails will also get along well with the fish, but might get eaten. If it is a marine comet fish, it will grow up to seven inches, and will also need a larger tank.
Mice live on land, fish live in water. On in not the normal prey of the other.
Your choice, check out your local pet store to see what you like. Check with the staff if you have any compatibility questions regarding putting different groups of fish together. If this is your first tank, start with a few community fish. A 30 gallon tank is a good size, easy to maintain, and large enough to enjoy many different fish. I started out with 2 - 30 gallon tanks, I've kept one tank with all different types of tetras (bleeding heart, glo-lite, neon, serpae, headlight/taillight, etc.) for over 20 years. Good luck.
Amount of fish in a tank depend on it's size and breed , if it is a medium Biorb then you can store up to 10 fish of 1inches and a bit. If you're planning of getting tropical fish, then install a heater and put 2 - 4 fish in at first. You can therefore add more gradually. If you are new to fish. Leave the tank for a recommended 2 weeks, then take a sample from the place you got your tank from. It should be fine.
He Revealed He Is Half Betta Fish.
it depends how big the tank is. since this type of fish stays relatively small, use the one inch of fish per gallon of water rule. mollies are a grouping fish and should be kept with 4-6 or more of their own kind. you can keep them with platies, guppies, swordtails, endlers livebearers.... many freshwater peacefull fish will 'play nicely' with them.
One gallon is really just too small for any type of fish, but 2.5 gallons or more would be great for a betta fish.
You don't! What you do is get a 55 gallon tank because angelfish won't be happy in a 10 gallon tank, and then you take the betta out of the tank (it will fight with your other fish) and just get more mollies and put lots of hiding places in the tank so the babies will live.
A short period comet.
That is small better stick with a goldfish.
Neons
The basic rule for keeping any kind of fish is. 1 inch of fish needs a minimum of 1 gallon of water.
A comet one stupid.
Which kind? Glass or acrylic?
You could put the following: 3x Neon Tetra or... 1x Betta
It depends on what kind of fish you are keeping; Goldfish and other 'cold water' fish prefer to be around 65-70F. Freshwater tropicals around 80F Marine tropicals around 78F
Depends on the kind and size of the fish. You should also take in to consideration how large they will get at adulthood. A good rule of thumb to go by is 1 gallon of water for every 1 inch of fish. So for example: 3 2" fish should be in at least 6 gallons of water. To be safe I would put them in a 10 gallon aquarium.
The basic rule for keeping any kind of fish is "1 inch of fish needs a minimum of 1 gallon of water." All fish tanks also need to have their water properly filtered to remove poisons created when a fish lives, breathes and poos in the water. No tank (pond?) is ever filled to the top so your nominal 2 gallon container is not big enough to keep any fish in without being cruel to the fish.