The opening of the procedures seem to indicate they're roaming relatively freely - as I gather this is not the case this should probably begin with a description of their containment environment and a mention that they are to be fed vertebrate animals at regular intervals.
I do need to flesh this out quite a bit. Since physical restraints tend to be more of a strong suggestion than a true limitation, I'm thinking it's better to keep them entertained and comfortable then to try and strictly lock them up.
Maybe I was also trying to get away from all the "locked in a steel vault/lead box, x by y by z etc." SCP's with something a little more gentle and cooperative. I might also want to add something about how trying to lock them in solid container might encourage them to start phasing through walls or something, making them harder to contain than if they're kept calm in an open room.
"brought in by a concerned citizen" - seems odd given its ethereal, hard to contain properties. Perhaps "brought to the Foundation's attention by a concerned citizen"?
My thoughts are that they have a somewhat cohesive body structure, meaning they tend to respond to physical boundaries, but take most of them as sorta negotiable if they're agitated. This one, having gorged itself at the fire, doesn't mind being coaxed into an aquarium and resting there for few days. I'll try and elaborate.
"lethargy and unresponsiveness among the cattle held there brought the creatures to the attention of the SCP foundation" - Foundation, but also seems terribly minor to attract their attention; a vet would probably be the first port of call
I sort of forgot steps in this section. I was thinking them, but I forgot to write them down. The owners of the slaughter house notice the creatures, and think they have some kind of vampire bats hanging around, they call animal control or exterminators, and one of those groups directly or indirectly informs the SCP.