My fish tank is unbalanced and killing fish. how do i fix this?

[stephenies]

I have a 55 gallon fish tank that i keep my fish in and a 10 gallon fish tank that i was keeping my guppies in. My 55 gallon tank has high NO2 and i cant seem to keep it down or make it go down. My 10 gallon water stays extremely foggy and has high NO2 as well. When i transferred my female guppies to the bigger tank to clean the 10 gal. all but one female died, but all the males are still alive as are the rest of my fish i have in the big tank. Is there anyway to balance the tank for the NO2 and get the water clear in the small tank? Ive tried the acuclear and changing the water for the foggy tank and the 55 gallon looks crystal clear and i did the same thing in it when i set it up.
i also have used a gravel vacuum and i had the guppies in the 10 when i first got them and put them into the 55. they are all in the 55 now. the water has been cloudy since i set up the tank and added fish. I change the water every week but only enough to get the nasty stuff out.
the 10 gallon tank is the only one that is cloudy.