Call Aqua POd and complain and they should send yu a new replacement fan since it should still be on warranty. HOWEVER...there is a quick remedy, and sometimes it will last for a long long time or maybe just go back to giving problems the next day.
First off gain access to the fan. Try blowing it out with compressed air. The little cans of compressed air they sell for blowing out computers etc work fine for this purpose. Give it a good blowing out. If it still howls or makes noise, if you look at the fan real close you will see one side of the fans in the middle has a label on it. It may say how many volts, the company name etc etc. Peel a corner of this label off so it exposes the end of the armature shaft and bearing under this label. Then take a tooth pick and dip it into some light oil such as 3 in 1 oil or sewing machine oil, or push come to shove some #10 weight engine oil. Use a tooth pick to pickup some oil, and then just touch the center portion of the bearing armature (will be exact center of fan assembly under label sticker) and allow some oil to wick off into the bearing. Allow to set a minute or two to soak into the bearing / bushing, and push label back on. This should fix the noise and get you back to shape long term. The problem is either the motor is caked up with lint and dirt or the bearing or bushing is dry.