You are changing a lot of water. Can you cut that back to like 25% per
week? I would never change 50-75% at a time unless I had serious
problems. Also do you clean/change your filter every time you clean the

tank? I wouldn't. Let the brown slimey stuff build up in the filter(s)
until it restricts flow. If you get a lot of debris in the filters,
brush it off into a trash can once a week if you must...... Otherwise
lightly clean the media just enough to regain flow.

I change that amount of water because the cloudiness gets progressively
worse if I leave it alone. I would like to change less, believe me :-)
I try to leave the filters alone and clean the sponge media about once
a month. I cleaned them recently in an effort to try and correct this
ongoing problem.

Same here. To original poster - also try cleaning the biological filter
media (sponges/etc.) in tank waste water freshly removed from the tank
- not
under tap water. Tap water has chlorine/chloramines and is awfully hard
to
get the temperature just right to not kill off the good bacteria in the

sponges/etc.. Since changing to tank waste water my tank has been
crystal
clear - even the silicate (diatoms) on the back and sides' glass is
going
away significantly, the diatoms were a hold over a year or two ago
around
the time started the tank and I am amazed it is finally going away.
Good
luck and later!

I appreciate both of the suggestions, I'll give it a try and see if
that helps. I did clean the sponge media in tap water and then added
dechlorinator directly to the filter to remove any excess
chorline/chloramines. However, per Spiral_72's advice, it sounds like I
should hold off on doing any additional cleaning of the sponge media.

Any idea what is causing the cloudiness though? Is it that I'm
dislodging bacteria into my tank and it has no where to attach itself
to?

One last thing I failed to mention is that the tubing to and from my
filters was caked with crud until recently. At first I thought maybe
the crud in the tubing (and it was thick) was causing the cloudy water,
but I flushed that out (using aquarium water) and then allowed the
filters to collect the stuff over the next 48 hours. After that is when
I cleaned the sponge media thoroughly (in tap water).

Thanks again for the advice!
Kevin