Particle problem with my tank

[TallShow]

I've been running my system for a while now. During the first 2 months, the water was crystal clear. Then out of nowhere, I saw these small particles floating around in the main tank. They look like dusty, white particles. Does anyone know what these are and how to get rid of them?

 

[Tahoe61]

Do you keep Gobies or Pistol shrimp?
Are you dosing anything?
Did you rinse the sand?
Have you moved power heads around?
Do you using any mechanical filtration like sock, floss or sponge?

 

[TallShow]

Do you keep Gobies or Pistol shrimp?
Are you dosing anything?
Did you rinse the sand?
Have you moved power heads around?
Do you using any mechanical filtration like sock, floss or sponge?

I have a few gobies. No pistol shrimp.
I dose every now and then.
Yes, I did.
I bought new powerheads recently. They've been in same position as the last ones, but are more powerful.
I use sponges. I don't know about socks and floss though.