Help! There’s a monster in my tank...

[CocoFish]

Hey y’all, so I just cleaned my fishtank and cycled it about 30% water after about a month. The tank stays consistently within 10ppm nitrates and takes care of itself pretty well. And it’s been running beautifully for about a year. Well, in only just 3 hours there is a stringy white substance ALL over the tank and caught in my beta’s fins. About 3 weeks ago I accidentally spilled way more food in the tank then I wanted. I was able to scoop most of it out. But the fish got a nice feast that day. They had a fast the next. No big deal. There was some leftover food under the black lid that only JUST started getting moldy, but it wasn’t horrible. I ended up cleaning that too. My other two tanks are completely fine as of writing this so it seems contained. And again, the tank was perfect. Now it looks like a spider threw up webs all over the place. Like a ghostly scene. What is this?? How do I get rid of it? It’s entirely covering the moss and I hope doesn’t kill it, but probably will, it looks bad. Do I need to strip the tank down and clean everything? Here’s a picture

 

[SomethingsFishy24]

If I had to guess it is a fungus. Which kind exactly that I can't say but fungal hyphae can look/collect in strange ways. Likely it is from the moldy food, even if it just began molding. I would hand clean all the visible white strands from all surfaces and then do a vacuum and at least 25% water change every other day for a week. A soft bristle tooth brush might work to wind the strands on it and clean it from the plant surfaces. You may have to uproot, "sanitize" and replant depending on how aggressive the fungi is.

 

[GaryE]

Some bacterial colonies flare up and fade, after looking like that. Biofilms. Or a fungus, as said above.
I would concentrate on clean water and it will probably fade out in a few days. It is kind of cool.