Fish tank looks milky

Milkyness indicates either a build up of bacteria (Bacterial Bloom) or suspended air bubbles in the water columb. If you have just changed the water, or just set up the tank, it will be air bubbles and these will eventually dissipate naturally. If it is the former then your water needs to be changed ASAP and the filter may need to be re-cycled. A complete strip down is what I would do under those circumstances. If you follow the basic rules of sucessfull fishkeeping which are. (:- 1 inch of fish must have at least 1 gallon of water. :- Every tank must have a permanently running 'cycled' filter. :- Every tank must have at least 50% of its water replaced every week.) these 'bacterial bloom' things should not happen.