Does anybody Know What This Is???

[Blind River Joe]

Hello:

This is my first post ever so I hope I am going this correctly. A bit of background info first. I have a large reef tank so sometimes I see things in there at night only as would be expected. Just tonight though I saw this animal in my tank and I can not figure out what it is. I have been keeping my salt water reef tank for going on four years now and have had the same 100lbs of live rock since day one. Nothing new has been added in the last 4 months so I don't think I have a hitchhiker from adding new items. The animal is defiantly light sensitive. I have attached a picture and would really appreciate it if some one out there has any ideas as to what this animal may be. The animal is kind of hard too see but if you look closely it is in the picture. It looks a bit like a coral but it defiantly moved just as I took the picture. The animal then disappeared back into the rocks. Look forward to learning new things from all the people out there.

Tank Size 250 Gallons

Lighting 750 watts halogen lighting

Tunze Wave Box

1/4 HP chiller

70 gallon sump

Skimmer

Don't really know what else to say