Extremely Clloudy Tank

Ive just got home from work and my tank is very very cloudy. When I went to work this morning I did a 15% water change and the water was crystal clear. Ive added pictures so you can see. (i took a picture of the clear tank this morning as I'm planning on selling it in the next week or so!)

this is before I went to work



and this is after....


As you can see there is a lot of difference so all advice would be appreciated.

Looks like a bacterial bloom. Find more information here http/www.fishforums.net/index.php?/topic/246850-bacterial-blooms-explained/

So came down this morning and the tank is perfectly clear again, could it have been just a mini bloom? all the fish look good and I tested the water and everything is normal!