I can't really tell how much its closed but here is a picture of it for you.....
I have it now sitting in around 24cm of water.
My fish stock is as follows...
2 tangs ( one large and one medium )
3 trigger fish ( two large and one medium )
2 Clown fish
6 Blue chromis
Feeding is pellets twice a day then mysis once , around 2-3 cubes.
If this happens again i will take a video this time before i turn off.
What i did notice tonight was in the clear plastic tube going from silencer to pump was air bubbles inside it? i don't know if this is normal or not.
Thank you