Are freshwater fish the same as tropical,and community fish?

These are two unrelated classifications you mentioned. Freshwater vs. saltwater refers, obviously, to the amount of salt in the water. Tropical vs. temperate refers to the temperature of the water, entirely independent of salinity. There are tropical and coldwater freshwater fish, there are tropical and coldwater marine fish. There is also a median between fresh and saltwater– brackish, and a median between tropical and temperate– subtropical.

“Community” fish is a misleading term used by pet stores so they can get off without knowing anything. A fish’s aggression is only relative to anothers. While Angels might be peaceful compared to other Cichlids, they probably shouldn’t be in your standard community tank. There is no single rule that can be used to stock a tank, so the number of fish you could put in your tank would depend on the fish you want, your filtration, and how much maintenance you’re willing to do.

EDIT: The opposite of a “community” tank would be an “aggressive” tank (how descriptive… right?)… a species tank could contain anything from Bass to Minnows. There are many coldwater-subtropical fish often sold as tropicals– Minnows, Dojo Loaches, Hillstream Loaches, many Geophagus species, and virtually all U.S. native fish fall into these categories. The “inch of fish per gallon” rule is total crap. Putting 20 Neon Tetras in a 20 gallon tank would probably be considered understocked, but a 15″ Oscar is insanity (according to the “rule”, it would be generous). There are far more factors than volume and fish length that go into stocking a tank.

Freshwater and tropical are generally the same thing. The only exception is goldfish, which are coldwater instead of tropical. Community fish are just fish that are for the most part peacefull and can be kept in tanks full of different fish, aka, community tanks. The opposite of a community tank would be a species tank, which only contains one type of fish, like piranhas, that wouldn’t get along well with other kinds of fish. The amount of fish you can put in your tank will depend on the type of fish. You could probably get a small group of cichlids, about 3, but then you can’t get many other fish. Another option would be to get a school of neon tetras, at least 6 of them. A school of otoclincus catfish, at least 3, and they will keep your glass clean of algae. Then you could add one or two dwarf gourami or powder blue gourami.

Yes, they are the same. Marine fish would be saltwater fish. I think the general rule is “1 inch of fish per gallon”……like, you could put 20 Neon Tetras in your tank because they’re about an inch long>>just an example. Here is some good info, regarding stocking and the levels fish like….some like to hang at the top, some middle, and some on the bottom:

some freshwater fish get stuck in the pump quick and tropical fish dont unless there about to die

No, they aren’t the same…:

Tropical fish: Fish that come from tropical regions that need a heater to keep their water at a warmer temperature. ex. guppies, tetras, gouramies, angel fish.

Freshwater fish: Fish that live in water that has NO salt in it. A.K.A fish that don’t live in the sea, or brackish (has a little bit of salt in it) water. ex. angelfish, tetras, goldfish.

Community fish: A group of fish that can live together peacefully, without any fighting. ex. guppies, platies, mollies and swordtails are community fish.

And the general rule for tanks is 1 inch per gallon. (So you could fit 20 one inch fish in your 20 gallon) But, there are some exceptions. Some fish just naturally need more room than others, so I would suggest that you put no more than 18 fish in your 20 gallon, even if they are guppies, (Which are an inch long)

Hope this helps!
If you have any more questions, just ask!
Good luck!

Freshwater fishes are classified into two groups tropical or coldwater fish. Tropical fishes would need to be in warmer water with temp of 72-82F, while coldwater fishes thrives in cooler water below 68F.
As a general rule you need to allot 1 gallon for every inch of tropical fish, considering their adult size as a gauge.