White powdery stuff in bottom of new pond

[Eva]

I set up my 110 gallon patio pond 10 days ago with city water. I put my UV filter in and in a couple of days the bottom of the pond and the filter are covered in what looks like fine white powder. Haven't put any chemicals in it, but today I took out the UV filter and put in a regular filter. Is this alge bloom? Or did my UV filter clean the city water and this is what's left? We do have hard water here. Do I need to wait before putting water plants in? I've had this pond 5 years and the first time I've encountered this.

 

[sissy]

Could be dead algae from the UV .No harm if it is

 

[Eva]

Could be dead algae from the UV .No harm if it is

Thank you Sissy. It's a lot of white.
The UV filter I took out is coated with the white stuff and is hard as a rock after drying. Could this be calcium?

 

[sissy]

could be also calcium but has any thing changed in your water .Do you have city water because it would show up in your house first .I would use quilt batting and stir it up so the batting in a crate with a pump pumping water into the crate catch's it .Seems to me since you did not see until after the uv makes me think it is algae A uv should not really clump calcium together .But I do know calcium does get hard but never saw algae really get hard after it has been treated either

 

[Mmathis]

@Eva Can you post some pictures?