A heater if you have tropical fish.. a good filter, lighting, airpump to make bubbles in case your filter doesn't produce enough, water conditioner to remove chemicals, gravel or sand made for fishtanks, and plenty of hiding places for fish (like pieces of PVC pipe). These are pretty much basics for all tanks.
ALL fish need filtration.
Yes all living things need to eat. Yes. You can buy fish flakes at a local pet store. There is no acception for fish. All living things need to eat.
All they need is a tank some water some rocks a plant and to be feed.
ok for a typical fish tank you will need a clean glass or plastic marbels or rocks. get a small plastic plant or other dec. to put in. you need dec. because fish like to hide. clean tank every 2 weeks or so. this answer is mainly for goldfish,betta & other small fresh water fish.
No, it really isn't fair at all. Some fish can survive in a small tank like bettas but they won't be happy. Fish need approx. 1 gallon per inch of fish to thrive.
You would need to put it in some sort of open container so that it didn't suffocate, but you would most likely need fish food fairly soon.
If by "clam" you mean a bivalve mollusc then the answer is yes they will live and grow in an aquarium. They do however need to be counted when working out the fish holding capacity of the tank. The basic rules are "1 inch of fish needs a minimum of 1 gallon of water" and "all aquaria containing living things must have a cycled filter".
depends on the size of the fish, there might not be enough oxigen in a small fish tank.
Scoop all your fishes to another tank or tub of water and clean the fish tank just as you would normally without the fish
Depending on what your sick goldfish has, it will either be specific to that fish, which you should place in a separate tank to treat, or it's something that will spread to other fish in your tank, in which case you will need to treat them all.
That sounds like my tank. If you have a filter then you need to replace or clean it on a regular basis. You may need to remove the fish from the tank and clean it. If you do then take some water from the tank that the fish are in and put it in another container. Take the fish out of their tank and put them in their old water in the new container. Drain all the old water out of the tank and rinse/wash all the rocks, gravel, plants, and other things that were in the tank. Wash the walls of the tank. Make sure that you rinse any soap off of the tank and the rocks and stuff before you put new water back in it. Fill the tank with clean water. You may need to treat the water for chlorine if you used city tap water. Do not put the fish back into the tank until the new water temperature is the same as the water they are in now. We don't want them to go into shock. You may want to buy a sucker fish and a couple of snails. They will eat the alge that grows on the glass and everything else. Good luck. I have to go clean my tank. Thanks for reminding me.
No. all fish need fins to swim. Or they would just stay at the bottom of the tank and die.