What makes water "thicker"

[CT_]

I remember in a video/live stream (or multiple?) cory mentioned that he can tell whats going on in a tank by how foamy the bubbles are.  I noticed both my home fish tanks and outdoor pond-tub have fairly "thick" water.  I put thick in quotes because I don't know if it has higher viscosity, but bubbles tend to be larger and they take longer to pop and my tank water wets surfaces differently (spreads out more).  I only noticed this when I setup a tiny shrimp tank on my desk at work (which has a different municipal water source) and noticed that I can get much finer bubbles out of a never clog air stone vs at home where the smallest I can get are about 2mm diameter.

 

So my question is, other than meds (I have no meds) what else can effect this?  I know there's a broad array of answers but what would be plausible/most probable?

[Daniel]

Proteins and other decomposing organic gunk is often in the form of long threads. This excess protein, et al can lead to bubbles taking longer to pop and even cause foam to form at the water's surface.

The difference in the size of the bubbles between the 2 airstone could be the difference in how tightly the airstones are screwed down against the felt pads.

[CT_]

WRT bubble size this seems to be the case with fresh water and I've tightened the bigger bubble one to max finger tight.

[Casual aquatics]

Purée 🤷‍♂️😆

[Cory]

Meds, protein films and ammonia are the most common ones.