fuzzy white stuff

Question
I have had my 30 gallon aquarium for a number of years. A few weeks ago a fuzzy white substance that grows all over everything, pieces break off and float and it has tendrils that come up started growing . I removed everything, scrubbed it, washed the gravel, put it all back in with fresh water. It came back. We have been putting these pills in it (turns the water green) and that will get rid of it for a time, then it comes back. It doesn't affect the fish at all. I have mollies, platys, tetras, neons and Chinese algae eaters which is what I have always had and occasionally swordfish, but none of these for about 6 months. I also have some catfish that I have had for years. Is there any way you can tell from this description what it is and how to get rid of it permanently? I am stumped. Thank you, June

Answer
Its a type of algae, is your tank in an area that receives full sunlight? also what do you have as far as scavenger fish (besides your catfish)? What you can do is wrap your aquarium in a dark sheet and do not turn on your aquarium lights for about 5 days (no this will not hurt your fish), cut your feeding down to once per day during this time and add some aquarium salt to the tank in the amount of 1 1/2 table spoons per gallon of water, after 5 days go ahead and remove the dark cover and do a 25% water change to help remove the excessive amount of salt, this will kill off the algae and help prevent it from coming back.  Make sure your doing weekly water changes as standard maintenance in the amount of 15 to 20%, this will also help.