Is goldfish a coldwater fish???
And what about neon tetra??
What is the difference between coldwater, freshwater, and tropical??

Goldfish are a coldwater fish meaning their ideal temp is about 72 degrees. A tropical fish normally likes temps from 78-84.

Freshwater fish live in water that has no salinity (salt). Salt water fish live in a high salinity enviroment, like the ocean.

If you are interested in keeping a particular kind of fish do all the research you can before you buy anything. That way you know if you can handle it or not.

I hope I have answered your questions, but if not feel free to ask more.

I am planning to buy the neon tetra. But I am not sure what do I need.
I planning this 20 gal kit:
Waterhome 20 Aquarium Kit
- 57.38 L
- 60 cm (23.6") x 30 cm (11.8") x 35 cm (13.8")
- Light Glo Fluorescent Canopy
- Fluorescent bulb
- AquaClear 150 Power Filter
- Radiant Heater
- Thermometer
- Plastic plants
- Fish Net
- Nutrafin Max Fish Food
- Cycle
- AquaPlus
- Waste Control
- Basic Aquarium Guide
- Video

I am going to add a 40gal air pump and some plant.
I am also planning to get like around 5 neon tetras(I will let then breed).
What else do I miss??

Maybe can you add my msn so I can ask you for more info about fishes.
This is my first getting fishes and I don't want them die><

Tropical: The tropics are the geographic region of the Earth centered on the equator and limited in latitude by the two tropics: the Tropic of Cancer in the north and the Tropic of Capricorn in the southern hemisphere.
en.wikipedia.org/wiki/Tropical

So basically any fish from there is tropical, be it saltwater or freshwater. Goldfish are not coldwater (as many people believe) or tropical, they are sub-tropical based on where they live.

Sub-tropical: The latitudinal zone between 23.5° and 34.0° in either hemisphere, bordering the tropical zone. Also can refer to vegetation, organisms, or weather typical of subtropical habitats.
biology.usgs.gov/s+t/SNT/noframe/zy198.htm

Well, you won't really need the guide or video, you have us for that. You can buy better fish food for about the same price. Cycle is not needed, but it may help get you started. You also do not need the waste control, water changes are always better

I recomend getting 6 first. They will feel more comfortable that way. Keep in mind they will not breed in hard or alkaline water.

I recomend cycling the tank before purchasing fish. Neons are very sensitive to poor water quality and will most likely die (or at least shorten their lifespans) if you use them to cycle. I don't know if you've been told about fishless cycling, but its fairly easy and MUCH less work. You can use cheap fish flakes or a bottle of liquid ammonia, whichever you preffer. The liquid ammonia must not have any added perfumes, soaps or surfactants. Add a tiny bit every day. If you are using flakes, do a 25% water change once a week. This will take about a month and a half. You will know when you are cycled when ammonia and nitrite are at 0, and nitrate significantly higher than the tap. Do a few waterchanges over the course of two days, then go get your fish

Things that you need that are not included in the kit is a test kit for pH, ammonia, nitrite and nitrate, a stand, and a syphon. Gravel would be nice too. Check prices on the necessities online at Petsmart and compare with the kit to see which is the better deal.

Thanks for the correction, sandtiger. I have always considered anything that doesn't get classified as tropical a coldwater fish.

Your welcome. In the world of fishkeeping goldfish pretty much are considered coldwater, I don't really like that because it leads people to believe that they cannot survive in warm water, being sub-tropical they can survive both.

Thank you for all your information guys..~^^
Well, this kit is actually the cheapest I can find in the city I am living in(I live in Richmond, BC Canada), so I may just buy the rest of stuffes that I miss..
I am really appreciate to all of you guys for the help!
For the tape and the guide, they come with the kit, so why bother keep them under my bed.
Once again, Thank very much to you all!

By the way, I miss one more question, what food should I feed the neon tetras?

A high quality flake food makes a good staple, like Omega One. Supplementing with meaty and veggie foods like brine shrimp, bloodworms, daphnia, and spirulina help keep the diet interesting

How do I know which one is the correct one?
I only saw those floating pellet for cichlids, goldfish.
But don't see any for the tetras.

I've never seen tetra-specific foods, but general tropical flakes fit their nutritional needs. I love Omega One, and I'm so excited that they have so many products now. They are only sold at Petsmart. Neons have tiny mouths, so get them flakes so you can cumble them to the apropriate size.

http://www.petsmart.com/global/search/search_results.jsp

For a staple, I would get the regular freshwater flakes or the supercolor flakes. They have a smaller size for about $3 in store. I couldn't imagine you needing more than that Those veggie flakes look good, I think I will try some of those. My black neons keep eating all of my oto's algae wafer