Why would my quarantine tote look like this?

[Chick-In-Of-TheSea]

Last treatment was salt. I noticed some of this debris here and there when the fish was in there. Fish hasn’t been in there for a few days. Opened the tote to clean it today and this is how it looked. 
 

There was charcoal in there but that was removed like a week ago and several water changes done since.

[ScottieB]

Totally normal, no worries! Its just mulm/detritus that settles out. I take that as a sign of a good ecosystem. 

[FLFishChik]

On 9/2/2022 at 3:28 PM, ScottieB said:

Totally normal, no worries! Its just mulm/detritus that settles out. I take that as a sign of a good ecosystem. 

Agreed. Now that there is little to no movement in the bin, the mulm has had a chance to settle without the fish/filter/ or anything else stirring it up. You’d be surprised how much waste some fish produce. We just don’t always see it because normally it falls down into the substrate or disperses into the water column. 

[Chick-In-Of-TheSea]

Seems like so much in just 3 days, and there was only 1 tiny black neon in there.

This dude was the only one living there.

[FLFishChik]

On 9/2/2022 at 3:40 PM, Chick-In-Of-TheSea said:

Seems like so much in just 3 days, and there was only 1 tiny black neon in there.

This dude was the only one living there.

Well, that’s different. Tell me about the sponge filter, was it cycled in another tank prior to being in the bin?

[Chick-In-Of-TheSea]

Yep. You know when I was cleaning that tote, black stuff was clinging to my arms. I think the sponge filter was collecting charcoal dust and then over time was purging it out?

[nabokovfan87]

On 9/2/2022 at 12:40 PM, Chick-In-Of-TheSea said:

Seems like so much in just 3 days, and there was only 1 tiny black neon in there.

This dude was the only one living there.

Feel the surface of the wood or anything that is similar (almond leaves, etc) and it should be similar in color.

It could be some "stuff" on the sponges given the color. I had one I had gotten recently that had some flakes from the manufacturing process and it isn't the easiest to remove all of those (it's like a 3d model plastic kit and there's little tabs stuck in some of the pores)

It wasn't a sponge filter, but a prefilter.

I'm going to say it's wood pulp.  And that you had good enough flow to deteriorate it during time in the tub. If no wood.... Then:

On 9/2/2022 at 1:46 PM, Chick-In-Of-TheSea said:

You know when I was cleaning that tote, black stuff was clinging to my arms. I think the sponge filter was collecting charcoal dust and then over time was purging it out?

Could be. Especially if there's no wood /botanicals in the tank to give off something that color.  Take the charcoal you had running if you still have it, then shake that off into a specimen container and see if it's similar.

[FLFishChik]

On 9/2/2022 at 4:46 PM, Chick-In-Of-TheSea said:

Yep. You know when I was cleaning that tote, black stuff was clinging to my arms. I think the sponge filter was collecting charcoal dust and then over time was purging it out?

I asked because I recently put a betta in a hospital tank with a cycled filter. Every day I had far more mulm on the glass bottom than a single betta who was fasting could possibly produce. I worked out it was detritus from the sponge filter . Weird.

[Chick-In-Of-TheSea]

All the stuff in the quarantine tank was fake. 1 silk plant, 1 plastic plant, store bought swim through cube. I don’t have the charcoal pouch anymore but this mulm stuff was definitely the same color as the charcoal. Black, not brown.