Ok... and for something not X-Treme at all... Here's a weird little sponge that has been growing in my prop tank. It originally came from my 90g softie tank that I took down. I've had these sponges for probably about 2 years, and they multiply pretty easily. Pretty cool orange mottled color, and they totally glow under actinics. They can grow to at least marble size... maybe even bigger. Trying to see if I can grow grapefruit sized ones Interesting to play with for filtration. Sponges are supposed to process a lot of water. And they pull silicates from the water for their spicules. Speak up if you want some!