Posted: Fri Dec 30, 2005 3:44 pm
The 1/4 water change every four weeks sounds like this is for an established tank of fish, not a tank with a turtle in it. (Remember, the mfgr is making recommendations thinking that the filter is being used with fish, not turtles.) I do partial water changes in my turtle's tank weekly, not monthly (I use an xP3 as well).
The nitrate, nitrite, etc. levels are all acceptable? (I would think your nitrate level would be somewhat high after a month with no water change and not that much water (33 gallons).)
Just curious, but what is the lighting like in the tank? Low lighting and/or dissolved organic matter can result in diatoms, sometimes mistakenly called brown algae. Otherwise, it could just be crud that needs to be cleaned.
If you are doing a partial water change, when you get the water out and the water level is lower, I'd just wipe off the brown stuff with a paper towel. You may find that it returns fairly quickly, though. The partial water change will alter the concentration of nutrients in the tank, but with the amount of water you have in the tank, you might want to do a cleaning and water change monthy - 5/6 weeks, depending on those partial water changes.
When I clean the XP3 tubing, I disconnect the tubes from the canister (it's too difficult to take the tubing off the other end) and push a small brush attached to a cord up the length of the tubing with a wooden dowel and pull the brush back down. I do this a few times until the tubing is clean.
As for the oily film on the water--are you feeding in the tank?
"You become responsible, forever, for what you have tamed." -Antoine de Saint Exupery-