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When I change the water do I change all the water or some of it. If I leave some in there how do I clean it because it will still be dirty. Where do I put the fish when I take them out? Also do I use tap water of the filtered water to refill the tank. The first time I tried it..I took out all the water then refilled the tank with tap water and half my fish died, so I really need some help

Additives such as chloramine added to tap water to sterilize it is bad for the fish. You should let the water stand for a few days before using it. Alternatively, if you live in an area that is not too industrialized, you might want to consider using rainwater instead.
It is also a good idea not to change all of the water (you should change no more than 40% of the water each time), as the fish suffer more stress the more water you change.

Im really down now..all my fish but 2 have died..I must have done something really wrong..If I am supposed to let the water stand for a few days what do I do with the fish for that time? Also if I only change part of the water then the rest of the water is still dirty..please help

I don't see the need to change all of the water in the tank at once. It's good to keep some aged ("dirty") water in the tank as it's good for the fish. I hardly ever change the water in my tanks and my fish have gotten along fine.
The water in your tank doesn't really need to be changed that frequently (unless you have goldfish). Changing all of the water at once will stress your fish enough that they may die.

I don't understand why you have changed the whole water. I do a water change every 10 days 25 to 33 % and I have never had problems.

If using tap water you should really use a anti chlorine and heavy metals treatment, the metals wont leave the water by just standing .
Also if you add water with chlorine to you,re tank water with ammonia in it turns into chloramines , which does not disappear with standing ..

Dont take your fish out of the tank. Siphon off water from the bottom of the tank (sucking up any waste you can find. Replace the water by siphoning it back in so as not to add too much too quickly. Use a Tap safe additive if you are using tap water to do water changes. leave the lights off for a while as well if you want. ( this helps reduce stress) Never change more than 40% as stated above and dont worry about the water thats left in the tank as this is being diluted by the fresh water. Depending on your setup you shouldnt need to change water too often.
I prefer to change very little ( about 10% every 3 or 4 days, this may be excessive!) change the water when you feel or know that Nitrate levels have risen too high. If your not sure of nitrate levels buy a nitrate test kit.
What size tank do you have and how many fish? Filter? What type of fish? How long has it been setup?
jason

I changed all the water because I did not know any better. This is my first aquarium.
The fish I had were some green corys and some panda catfish. I had the tank set up about a month..then I changed all the water and replaced it with tap water guess thats why my fish died..I HAVE TWO CATFISH LEFT THEY ARE NOT MOVING BUT STILL ALIVE WHAT CAN I DO TO HELP THEM?

I would pretty much leave them be at the moment, since anything you do will most likely worsen the situation.

I hope for you that they will be OK again soon, but please don't change the water any more now for a longer time!

Few things we need to know.
What sort of filter are you using?
Temperature of the water?
Have you cycled this aquarium properly?

I dont know what kind of filter its just a small filter that came with the aquarium in a kit. The water temp. is about 78 right now. what do you mean by cycled this aquarium properly?

thanks

Read this, it will explain it to you.
http://www.corydorasworld.com/ken.htm

Whoa! This will be difficult. ShawnM311 is a newbie. His cleaning method is how I used to do it when I was a newbie during the early to mid 70s. Unfortunately, the common layman thinks that cleaning the tank means taking out the fish, putting them in new water straight from tap then, stripping down the whole tank for "cleaning" using a lot of tap water again. Everyone has to start somewhere.

Listen to jscoggs27. If I am not mistaken, he knows a lot about discussions on new tanks. I read his posts on another site. I shall name some sites here for you to try out. Most of what I will post will have newbie forums in them. I shall also post some sites on "cycling" tanks. Read through them and don't get fish until the tanks are fully cycled.

General Freshwater Sites:

http://www.aquariacentral.com/forums/
http://www.aquahobby.com/board.html
http://www.fishforums.com/phpBB/index.p ... db7fa2f6fa
http://www.aqualinkwebforum.com/6/ubb.x ... 8126047912

Cycling Sites:

http://freshaquarium.about.com/gi/dynam ... dware.html
http://www.duboisi.com/nts1.htm
http://www.tomgriffin.com/aquamag/cycling.html
http://www.tomgriffin.com/aquamag/cycle2.html

What was the problem with the link I posted to the Cycling article on my site???
http://www.corydorasworld.com/ken.htm
It fully explains the process, there is also a link to my forums where we would be happy to help.

Its true. Tims site has some very good and easy to understand articles on fish keeping and disease treatments.

Thanks all the links are helpfull some are a little hard to understand since I am new to this but I have learned from them. Thanks guys