Hi,
First of all, you should NEVER have to tear down and "clean" your tank. Clean the filter, do a PARTIAL water change, (10-25%) and use a high tech tool called a scraper, (razor blade on a stick) to clean the glass. Or a sponge on a stick, what ever works.
Thats it!
"Slime" is natural.
Without boring you too much, you do need to understand any tank has to "cycle."
When you first set it up, it's steryl. As soon as you add something alive, say a small fish, that fish eats, and well... poops, and chemical changes start happening right away.
First amonia builds up. Bacteria catches up. This is GOOD! You WANT this.
That benificial bacteria breaks down amonia into nitrites. And eventually into nitrates. Each step is less and less toxic. Eventually the whole thing reaches a balance. That "slime" is a film of bacteria that will grow on every surface in there.
Some filter systems depend on this. Undergravel filters for example. Some filter media is nothing more than wierd shaped bits of plastic or other material with a lot of surface area for that bacteria to grow on and act as your filter. Don't worry so much about it. keep the glass clean, and if you can't stand it on a decoration, clean that. So you know also, "good bacteria" keeps the tank clean. And a clean tank smells like garden soil. If it smells like rotten eggs, you have bad bacteria starting. Poor filtration, overfeeding, or not doing water changes will cause this.
Unless..... the only other thing that would cause a build up of "white stuff" is over feeding. Uneaten food will start to grow nasty things on it.
Rule for fish feeding, is they eat EVERYTHING in three minutes. You can feed often, just tiny amounts. Fish nibble all day in the wild.
Hope this helps.