OK mistake number 2. Compounded upon the first mistake, I now went ahead and used spring water. The logic being, "its good drinking water, it must be OK for the aquarium". And hello cloudiness. I just couldn't work out what was going on. Time to do some more reading. I kept coming across comments about water hardness and they rang true. So I got onto eBay & bought a hardness kit. Tested, and the hardness was so high the kit couldn't measure it.
The picture above shows the tank on the slow return from opaqueness. At this point I was doing 50 litre, approximately 25% water changes daily. And slowly, slowly it came back. My poor fish deserve a medal.
Tomorrow we will look at mistake # 3.