Why is my cold water fish tank gone white cloudy ?

Hi I got a nice fish tank 60cm x 30cm x 35cm from my friend. I cleaned it when I got it with hot water, then it "sat" in my room for about 4 months. I finally decided to get fish I have: 5x Long-fin Danio and 2x Red Fantail Goldfish and I put 2x Vallisenaria plants (i don't know the names I have it on my receipt :P) and a 101F Aqua One Submersible filter (i have an air tube to it so that there is air in the tank). I also have pebbles off the shore xD im on low budget here hehe I put them in an oven to get rid off the bacteria and then I rinsed them off. I used tap water in my tank (the local fish shop person said it will be fine) I didn't do any special filtration cycles with special liquids or measure the PH in the water (budget). The water was clear until a day after I put the fish in the tank... The filter is good 350l/h so I don't know whats wrong. The water is sort of cloudy white colour, I read on the web about bloom and stuff but I don't quite understand it :( Can anyone help ??? It would be really nice :D