Are you getting your water from the tap faucet? How are you adding the water to the tank? Some aerators on a faucet create micro bubbles that will make your water appear cloudy until they go away.
I get this if I'm not careful when I use my cheesy WC change method. I don't have a python or a faucet big enough to use with a bucket, so I use a gavel vac backwards to divert water from my kitchen faucet to a bucket for water changes. If I stick the gravel vac all the way over the faucet and submerge the outlet, my bucket of water becomes instantly cloudy due to the micro bubbles the aerator creates. If the outlet is not sumberged, I can watch the cloud of micro bubbles flushed out of the vac and into my bucket.
Just a thought