white stuff growing at bottom of thank?

[KittenFishMom]

In my plastic tote tank, I have notice some white stuff that seems to be growing on the edge of the stuff on the bottom, a bit of dead hornwort, some stones, etc. It kind of looks like it settled there. the tote/tub is sitting on a board on a blue frame.

When I tested the water, there was less than 0.5 ppm ammonia, and almost 0 nitrates and nitrites. The tank has a bit of a swampy smell when I lift the cover. I will be doing a water change after I post this. It contains 1 male betta, 2 blue neon tetras that I need to catch and move to the tank with the other neon tetras, and 5 guppies and a few guppy fry. This tank has been cycled for 2 or 3 months. 

This photos are cloudy because it is in a plastic tote, not glass. I will try taking some from the open top as well.

Any idea what this might be?

This is photo from above. the white stuff is on the edge of one of the IAL. the driftwood is covered with snail eggs.

The white ceramic ring in this photo is the same one in the photo above.

Edited February 23, 2022 by KittenFishMom
added view from above

[Ken Burke]

Hard to tell, but looks like bio-film to me.  

[KittenFishMom]

@Ken Burke Do I need to do anything about it? I didn't know you could get biofilm on the bottom, I thought it only floated on top.

[Ken Burke]

If it is biofilm, no action needed.  Normally it is harmless and critters like shrimp will eat it.  Given some time it will go away.

[KittenFishMom]

@Ken Burke Thank.

The water and solids smelled a bit funky when I vacuumed it out during the water change. I cleaned the sponge filter too.  All the fish including the guppy fry are looking and acting normal.

[Ken Burke]

Keep an eye on it, but you should be ok.