Pinhead size blue dots

[Lynnzer]

I was about to do a water change on one of my tanks this afternoon but before I started I saw a myriad of small blue dots that are moving slowly around the glass. They are obviously free agents of some sort rather than the usual stick in place algae. They are also in various sizes from a pin prick up to pin head.
What the hell are they? More importantly are they dangerous and what's the best way to get rid om them if they are

.

 

[Colin_T]

Can't tell from the picture but they are probably harmless. Most organisms that affect fish are microscopic or don't look like that.

If you are concerned, wipe the glass down with a clean fish sponge, do a 75% water change and gravel clean the substrate. That should remove most of them from the tank.
Make sure any new water is free of chlorine/ chloramine before it's added to the tank.

 

[Sgooosh]

snail?