Any clue what this is?

[Kain]

First hello i am new here

Second I have a 29 Gallon Biocube and pretty much new to this as i have had my tank a year now.

Anyways my pump was blowing air bubbles out of it over night (maybe 10 hours) while I was away for the night cause my filter got clogged and 3 of my snails have now flipped over upside down.They are still moving some and I flipped them over again , but they not really moving.Maybe Dying, don't like alot of oxygen? Only things that seem like they got affected.

So one of them was wedged between some LR and I had to move the rock. When i moved it i found this, which i have no idea what it is. Good ,Bad ,Name?Any information would be great. Picture provided below

Thank you in advance