What Is This "goop" And Possible Cause?

[TheShrimpGirl]

I set up a nice 20 gallon tank at grandmas about 3 weeks ago, upgraded from the 8 gal I gave her. About a week and a half ago I noticed this goop/slime growing on the filter biowheel and lid. It started out as just a small patch and in the last couple of days it has really started to grow and now covers the half of the tank hood where most the condensation collects. 
 
I'm not really sure what it is or how to solve the problem. It doesn't seem to be effecting the fish much, but it grosses grandma out, lol.
 
The water stats are all normal accept for the ammonia which was a little high, so I did a 50% water change. When I set up the tank for her I transferred the filter medium over from the established 8 gal tank, so the cycling should be fine. She has it stocked with 7 neons and 4 male fantailed guppies with a colony of about 10 ramshorn snails. For plants she has a very large clump of java moss and a bit of parrot's feather. The filter is a penguin 20 gallon filter with biowheel. 
 
Here are some pics of the slime. It appears to be a residue of some sort that gathers as the water evaporates. Our water here is pretty soft, but it could possibly be a mineral deposit?
 
 

This is the filter lid near the out take end below the biowheel.
 

This is the side of the biowheel where it collected.
 

The underside of the tank hood.
 

 

[BerryAttack]

on the wheel part i thought of it being calcium build up, but then looking at the other pics it doesn't... very strange, first time seeing this.
most likely some kind of algae/fungus thing?
remove it and scrub everything where it grows and clean with vinegar water solution. 
 
hope someone else can help expand on this, all the best.

 

[DreamertK]

Looks like bacterial colonies, particularly if the wheel doesn't move and/or the water in that general region is pretty static. You should test for NH3 some time after cleaning it. I doubt it's the same bacteria, but you never know.