Guppies, Platties, Swordtails and Mollies. there are a few others, but you likely won't see them in the aquarium trade.
yes. please provide tips on fresh water aquarium fish too.
As a decoration, maybe. As a living entity--NOPE.
This link lists the most common fresh water aquarium fish (excludes salt water fish), there are hundreds.
If it is a fresh water fish than it isn't really meant for salt water. Do some research on the breed of the fish though because some can survive in salt water.
In most cases, no. The fish will die.
It is not recommended to mix salt water fish and fresh water fish. It is required to separate the two and provide each with the proper tempered water.
the marine fish would pretty much suffocate and die. so putting marine fish in fresh water is not a good idea.
Done frequently, and easily with many species.
They're designed for salt water, not fresh water! Just the way they are made. You can get aquarium salt from your local pet store, but don't put any in there if you have other freshwater fish that don't need it. Or get a tropical freshwater fish like mollies instead!
Explain what would happen if a piece of seaweed from the ocean was placed in a fresh water aquarium?
If you wish a fresh water fish to be kept alive and well so that it may be studied or kept as a pet. The fish will need to be placed in a suitable container with suitable water that has suitable parameters. Without water a fish will die just like you would die if your air supply was removed. If the fish was a fresh water fish and the water was salt as opposed to fresh, to the fish, it would be similar to what would happen to you if someone put poisoned gas in your personal air supply. You would be extremely ill and then die. So would the fish.
The difference is the salt concentration in the water. Fresh water aquariums mimic the environment of lakes, ponds, or rivers. However, salt water aquariums have water that is salty like oceans. Fish are either freshwater or saltwater. Do not put them in the wrong water, or they will die.