Is this some kind of algae, hydroids or what...

[Reef Wizard]

Can someone help me id what this stuff is? It is white and its growing on the back wall and corner of the overflow box. These are the best pic I can get of it with white lighting on
Thanks,

 

[ISpeakForTheSeas]

Sponges - harmless filter-feeders.

 

[Reef Wizard]

Sponges - harmless filter-feeders.

So leaving them is fine? I guess if they start taking over then I can cull them

 

[ISpeakForTheSeas]

So leaving them is fine? I guess if they start taking over then I can cull them

Yeah, as long as they're not gunking up the plumbing/equipment, they're totally fine/beneficial to leave - some people purposefully keep sponges as cryptic filtration.

 

[Reef Wizard]

Yeah, as long as they're not gunking up the plumbing/equipment, they're totally fine/beneficial to leave - some people purposefully keep sponges as cryptic filtration.

So these have spread all over the rock work and Its fine now but in case it gets overruling is there anything that eats this?

 

[ISpeakForTheSeas]

So these have spread all over the rock work and Its fine now but in case it gets overruling is there anything that eats this?

Yes and no (I apologize for the huge blocks of text below):

Lots of things will eat sponges, but I don’t know if any of them (that won’t starve like nudibranchs would) are totally reef-safe - almost anything that might eat sponges are a risk to corals too (and, in some cases, inverts as well). Beyond that, not every sponge eating critter will eat every sponge, so there’s no guarantee any critter you get would eat the sponges you want them to.

To quote another of my posts:

Manual removal is almost certainly your best option here (for why, see the first quote below, for manual removal control ideas, see the other two):

Just to put this out there - the problem with using biological controls (i.e. something that eats it) with sponges is that there are a ton of different sponges, some of which look indistinguishable from others. Some of these sponges are inedible or extremely undesirable foods to some species (either because of chemical defenses* or just because of taste preferences) while being highly desirable to other species. So, even if you pull in a known sponge-eating species of fish/starfish/whatever, there's no guarantee it will eat the sponge you want it to eat. Also, many of these sponge-eating species eat other things (like coral) that you might not want them eating.

Long story short, manual removal is probably your best option for sponges until more study has been on both specific sponges and specific sponge-eaters, but you can try it if you want.

*Just as a note on the chemical defenses of sponges, many sponges produce chemicals to avoid being eaten. Some of these chemicals are more generalized, some of them are specifically anti-fish, some are specifically anti-echinoderm (starfish, urchin, etc.), etc. So, again, some things might eat one sponge but not another, and because of the whole indistinguishable thing mentioned above, the sponges that are and are not being eaten may look pretty much identical (some may be distinguished/ID'ed under microscopic investigation, others may need to be DNA tested to be distinguished/ID'ed).

Just my two cents here.

All of that said, if you’re really determined to try biological controls (i.e. predation) for your sponges, here are some known sponge eaters you might be able to find in the hobby:

-Angelfish (particularly large angels, from what I’ve seen)

-The pencil urchin Eucidaris tribuloides*

-Starfish (quite a few different species eat sponges, but not all of them do; aside from Aquilonastra starfish - known in the hobby as Asterina starfish - starfish have abysmal survival rates past ~8-13 months, so I’d suggest to avoid these)

-Moorish Idols (these have abysmal survival rates pretty much regardless of how long they’ve been in captivity, so I can’t recommend them either)

-Nudibranchs (they only eat like 1 to 4 specific species of sponge total, and they will not branch out beyond those species - please do not buy these, they will starve)

-Some trunkfish and (typically large) filefish reportedly eat sponges (and inverts)

I’m sure there are some other species I’ve missed (particularly fish species), but that pretty well covers the known sponge eaters.

*Info on the pencil urchin diet:

What is this? Reef safe?

Pls help I’d and lmk if safe or not

www.reef2reef.com

For manual removal:

To add, some sponges have incredible regenerative capabilities, so multiple removals may be necessary, and doing what you can to minimize the odds of remaining sponge cells ending up back in your tank is recommended

I've heard of some good removal success rates with the injection method (described below),

The best way I've heard to control sponge growth at this point is to use a steel straw to scrape and siphon out the sponge you want to remove. Sometimes you can create bad conditions for them and kill them off that way, but that's typically much harder and not always effective.

I would try the scraping with a steel straw/brushing with a toothbrush and siphoning out for that one in particular - if you can do this is a bowl of saltwater out of the tank (I don't recommend adding the water to the tank after) and rinse with clean saltwater (not from the bowl) afterwards, that would be even better.

I should clarify here - the scraping and siphoning method I refer to literally siphons through the straw as you scrape to try and prevent spreading (this is also why I recommend doing this in a bowl outside of the tank).

Some other sponge removal methods:

Other suggestions include exposing the sponge to air (obviously not a guaranteed solution, and definitely not viable for this situation); hydrogen peroxide dipping the sponge (again, not viable here); injecting the sponge with hydrogen peroxide, vinegar, boiling water, or air; microbubbles in the display; and a few more. Predation is not usually a good solution for this issue

Basically, if the sponges have enough food and enough trace elements (which for most sponges includes silicates) to meet their needs, then you’ll see their populations booming.

If you can figure out what’s allowing them to thrive in your tank, then you can deal with that root cause and get rid of them.