I have a brand new 4ft freshwater tropical community tank. I noticed that after a few days the usual 'cloudiness' that you experience after a water change was not going away - in fact it was getting worse. I changed the water again and the cloudiness appearend immediately, the water change made no difference. The cloudiness was a greeny/ browny haze hanging in the tank. I changed the water daily for a fortnight and this greeny/browny haze persisted so I emptied the tank and bought another load of new gravel and the problem has come back. I have kept fish for 35 years and experienced some algal issues over the years but I have never seen anything like this before and am at a loss to explain it. Any ideas?
In my experience those symptoms indicate that at some time of the day the sun shines directly into part of the tank. Changing the water only the water only aggravates the problem as it is new nutrients for the algae.
If it is not possible to change the aquariums position, you may want to consider covering side/part of the tank that gets the sun, and/or a UV filter which should clean up the water.
What you say Wildwood makes sense but the position the new tank is in is exacty where the previous tank was for 21 years. The old tank split and I bought one of the same dimensions to replace it. Never had a problem in the old tank