Help ID dust/slime/spong like thingy.

[Fjdam]

Please help.me to ID what is this thing. This thing attached to only 2 LR.. other rocks are fine. Im not sure this is detrius caught of slime or what. Not sure if it will spread to other rocks.

[DottyClown]

Should be either diatoms or dinoflagellates.  Your tank is still new or cycling?

Just siphon them out during water change(s).  They should all go away with time, once your water paramenters are good.

[hazelnut]

you could up your flow in that particular area. it should clear up. it attaches on the rock due to low flow.