Newbie here, what is this ?

[scmang]

This tank was a disaster but about a year old, I have replaced water, did water changes, added sand and rock (couple weeks apart), added hermits and snails,but same fish are in there. Water is testing with salinity 1.026 nitrates and nitrates at 0. Only fowlr

 

[saltytanked]

Look like diatoms which are normal in a newer tank usually