1. Describe the clear stuff:
* Appearance: Is it stringy, fuzzy, slimy, or filmy?
* Location: Where is it growing? On the glass, on plants, on decorations, or floating in the water?
* Texture: Does it feel smooth, rough, or sticky?
* Movement: Does it move or sway with the water current?
2. Tell me about your tank:
* Size: How many gallons is your tank?
* Fish: What types of fish do you have?
* Plants: Are there any live plants in the tank?
* Maintenance: How often do you clean the tank and change the water?
Once I have this information, I can give you a better idea of what the clear stuff might be and how to deal with it.