Is this a sponge? 11/19/08 Hello Bob, <Mich here in Bob's stead> I'm in desperate need of your help to identify a nuisance substance which has infested my live rock and killed several corals. <Mmm, more likely the symptom of a problem rather than the problem in and of it's self.> More importantly, how to get rid of it or what eats it. <This is likely the root of your problem.> I have been battling this stuff for a few years now in my 240 gallon reef tank. <Sponges are not inherently bad.> Last summer I gave up the fight and had to destroy a lot of live rock. <Mmm, most unwise.> To my disappointment, last week I noticed another infected rock. <Is not "infected", is a natural part of the reef system.> There are three different forms of this stuff: Black, white and yellow. <And likely many more forms in most established reef systems.> All three grow like a skin covering the rock. <Yes.> The yellow and white are slimy and smooth to the touch. The most common and most difficult to kill is the black. The black actually looks like it could be a sponge because it has very tiny holes. <All your photos show sponges.> When I cut into it, the inners are a white gooey substance. <Heee! That just sounds nasty ;) > It feels and cuts like flesh. <And nastier!> It is very difficult to remove from the rock. <Yes.> It will kill my corals. <Unlikely, there are some types that are harmful to corals such as boring sponges, but most won't. It does look like you might have some photosynthetic sponges growing, if you find they are impeding the growth of the coral then you should trim the sponge back.> It infects the base of the coral (Acro, Galaxy) and in turn the coral starts to die. <Mmm, if there is open skeleton the sponge may grow there or around the live rock, but it is rare for sponge to kill coral.> I had to frag several corals to salvage them. <I'm surprised you had to go to this length. Simply lifting the coral out of the tank and exposing the sponge to air often kills sponges, but then you should remove as much of the sponge as you can so as it decays it doesn't pollute the tank. But again, I highly doubt the sponge is the root cause of your problem.> I have tried to kill this stuff by leaving the rocks out to dry, removal with a small knife, using a dental pick and brushing the infected areas with a tooth brush soaking in vinegar. Also tried soaking the infected areas with Lugol's iodine. To my surprise, this stuff survives and comes back in the same places. <It is normal and natural for sponge to be present in your system, particular in the darker recesses.> I suspect it has bored into the rock. My last resort was boiling the rocks in a large pot on the BBQ for 15 minutes, then using the pressure washer to scrub rocks. <Oh my! That's like killing spiders with hand grenades. You're killing something potentially beneficial and doing a lot of collateral damage.> I thought I had cleared my tank of this stuff, until I noticed another infected rock the other day. Can you help? <I hope. Excessive sponge growth can be a sign of excess nutrients, but I'm not sure you even have excessive sponge growth. Your photos show what looks like normal sponge growth to me. Excessive sponge growth is typically associated with excessive nutrients. I am curious as to your husbandry. I have included several articles that you may find beneficial below. http://www.wetwebmedia.com/sponges.htm http://www.wetwebmedia.com/liverock1.htm http://www.wetwebmedia.com/scottsh2ochgart.htm http://www.wetwebmedia.com/water.htm http://www.wetwebmedia.com/watrqualmar.htm http://www.wetwebmedia.com/marine/maintenance/marineMaint.htm http://www.wetwebmedia.com/toxictk.htm > Thanks, Greg from Ontario, Canada <Welcome,
Mich from Gouldsboro, Pennsylvania >

Re: Unknown organism    9/20/08 Hi Bob...Thanks for the response. Would you suggest feeding some of the sponges to my Imperator angelfish? Thanks again Peter <Worth trying. BobF>