White stings appeared overnight on tank wall

[DickCleveland]

I think I may have them ID’d but this morning roughly 15-20 small with strings appeared mostly on the black plastic tank back but one on the front glass as well please see pics below.

Water Parameters as of 1/1:
salinity 1.024 (refraction)
PH 8.2 (api)
Ca 500ppm (api)
KH 11 (api)
PO4 less then 1.0 (api)
NO2 0 (api)
NO3 0 (api)
NH3/NH4 less then 0.25 (api) may be error or as a result of tap water, additional test kit being researched. Recently switched to seachem prime from api water conditioner
MG n/a (saliefrt)

images:

 

[Saltyreef]

Those look like digitate hydroids. Best if you can scrape them off at the base while performing a water change so you can suck em out.
They are invasive and will sting corals.


Also, tap water isnt the smartest choice for a reef tank with coral.
Youll be better off with machine dispensed RO water from a supermarket or corner water machine.