How to distinguish between beneficial bacteria and bacteria?

[usbmouse]

I had issues with some bacteria before, tried to run rwdc for couple of days only with clean water and beneficial bacteria (great white)
I see brown residue on pump and pipes, and that makes me wonder - did the infection survived? Or how does beneficial bacteria should look like? Does beneficial bacteria change the water or leaves residue?

 

[Smokey0418]

I’m no expert in what bacteria looks like but I definitely run it.

I am going to say that the residue is definitely bacteria.

I run a power head in my reservoir and if I left the filter on, over time it would fill will brown and if I’m not mistaken I remember reading about how one could use the sponge in the filter to trap bacteria to hold and or transfer.

So I’m going with bacteria , the good one.