This question has been asked a lot and i search the web looking for answer, i found some, but not everything so i’m asking the complete question here.

I had 2 fishes, I don’t know there names, one has a orange color and the other has a yellow or golden color ( but not the golden fish) the yellow one died yesterday and the orange one is still living, fishes are so cheap in my country, i can buy any fish for less than 1$ so I’m gonna buy other fishes and buy a bigger tank (about 40 cm by 30m) is this enough for 3 fishes? and I’m gonna buy the equipments that are show here:

http://www.wikihow.com/Make-a-Goldfish-Live-for-Decades

are they good? are they expensive? and are they necessary?

But now I got one fish left, I don’t care if it dies because i’m gonna buy other fishes but I want to know how to treat it because I don’t want to buy fishes every 3 days so I’ll tell you how I’m treating it and tell me if this right or wrong plz :

the 2 fishes where living in a tank that has no equipments whatsoever (just for now, i’ll buy a new one) it’s a small one about 20cm by 10 cm or so, so they can’t swim that much, we where changing the water every 2 days and filling the tank with drinkable water which is so clean because we bought a machine that costs 1000$ to purify the water. And the tank is decorated as shown in the link above (pretty much)

the 2 fishes eat once a day ( because i google it and they said on yahoo answers to feed them once a day but they didn’t say how much) i was giving them a 1 cm peace of food that has a thinness less than 1mm, i crushed it in my hand and throw it, but now since the other fish is dead i’m trying to feed the other one 2 times per day and the food looks like this ( pretty much)

http://joshmadison.com/notebook/close-up-photo-fish-food/

And the water Temperature I don’t know but the temperature in my home now is 30 degree or so C in the summer, and in the winter it drops to 10 degree C or so (I’m talking about the maximum and the minimum) I suggested to mix the water of the tank with some cold water because these fishes live in the river and the river water is cold, is it a good move? I introduce cold water to the tank once a day so it will eventually become hot, i started to do so, when my other fish died, so i’m doing experiments on the one that is still alive. and I noticed that the 2 fishes spend the day on the surface of the water, it’s like they want to breath, why?

Tell me if what I’m doing is right and tell me if I should do anything more, if i forgot to do something, because I don’t want to keep buying more fish, so I will do everything you tell me and test it on the fish that is alive, learn from the results and then buy the other fish. Thanks