What is this on the glass of my tank ?

[Shayxoxoxox]

It’s this brown looking stuff. I’m assuming it’s algae, not sure if it’s healhty to put my Axie in the tank because of this. My tank is new and just finished cycling. I do not have any substrate/plants/decorations in it as I had a whole bunch of stuff before and it was wrong for my Axie. My nitrates are high and I’m just trying to bring them down with water changes but this brown/reddish stuff will not scrape off with a algae sponge and scraper. What do I do ? Is it harmful to my Axie ? Thank you very much, I appreciate anyone’s answers and I’m still trying to learn to use this amazing site

 

[Wyvell]

looks like Algea to me. I have had similar stuff in my tank for as long as I can remember. Should be fine for the Axolotl to inhabit.