Most of us only use the charcoal to remove medications when they have been used as the charcoal loses its effectiveness after a couple of days no matter what. No do not worry about changing it. Just leave it there and if you need to use medicine then you can add some if you need to. Otherwise just forget it is there.
They are get to looking REALLY gross. You have not seen gross until you have seen what a Bio-wheel gets to looking like. All you do is just take the USED TANK WATER when you change your water in the tank and swish it through the water softly and just knock off the worst of it. You do not even do that every time. Believe me, unless it has a lot of stuff on it, some of the algae stuff is not going to hurt anything and some of the bacterial growths can look like algae growth.
You may want to do a 30% water change and try to concentrate on taking the top water if you can. Just to get the film off the top of the water (or try to) - skim the top off the water. It is not going to clear the water but it may help a bit with the film.
What is the dechlorinator that you use? If it is StressCoat you may be using too much. It contains aloe and it does not evaporate and sometimes if it is not measured carefully the water can get "slick" with the aloe.
Angel sounds like an"angel" indeed. She is a keeper for sure. Enjoy her. She obviously loves you and feels safe and contented or she would not act the way she does.
Enjoy.
Rose
