Can anyone diagnose this? Growth on rocks

[Valdiviuh]

Hello everyone,

My friend’s tank has had this white growth on the rocks for about a month & recently have gotten progressively worse. They have different shapes, some look pointy & other more like bulbs. Can anyone diagnose what it is? & give us some information on it. Thank you

 

[wakejumper22]

Pretty sure they are tunicates

 

[west co reefer]

+1 Tunicates

 

[Valdiviuh]

Pretty sure they are tunicates

Do you know anything more about them? I looked up other threads just now but there’s not much. Are they harmless ? I have several colonies spread throughout the entire aquascape

 

[ISpeakForTheSeas]

Hello everyone,

My friend’s tank has had this white growth on the rocks for about a month & recently have gotten progressively worse. They have different shapes, some look pointy & other more like bulbs. Can anyone diagnose what it is? & give us some information on it. Thank you

Those are pineapple sponges (genus Sycon) and another kind of sponge - pineapple sponges are harmless filter-feeders that typically boom then bust in population and go away on their own after a while; the vast majority of other sponges are also harmless filter-feeders, but a few may be invasive and/or chemically harmful to corals:

Yeah, that's definitely a sponge. Most sponges are completely harmless/beneficial, but some can be invasive and/or harmful to corals (thankfully, these are rare).

To tell if a sponge is chemically harmful: if a healthy, established coral starts closing up or looking to be in bad shape on the side closest to the sponge as the sponge grows closer to it, and nothing else has happened (lighting changes, parameter swings, pests, etc.) that could explain it, then the sponge is probably chemically harmful.

Chemically harmful sponges are very rare.

For invasive sponges: unless it shows signs of being chemically harmful or starts actively growing over and smothering a coral's flesh/polyps, it's harmless. These can grow over the skeletons of corals, around the base/stalks of corals, even up into the water column above corals (where they're over the coral but not growing on the flesh or polyps themselves), etc. without harming the coral at all - as long as the coral flesh and polyps can get food, light, and flow, the sponge is harmless.

Invasive sponges are moderately rare.

Invasive and chemically harmful sponges are incredibly rare.

Also, for what it's worth, tunicates are also filter-feeders; some of the colonial tunicate species are invasive enough to smother corals, but if they're isolated, you should be able to contain the spread and prevent any issues. Outside of those invasive species, though, tunicates (both colonial and solitary) are harmless.

 

[Valdiviuh]

Those are pineapple sponges (genus Sycon) and another kind of sponge - pineapple sponges are harmless filter-feeders that typically boom then bust in population and go away on their own after a while; the vast majority of other sponges are also harmless filter-feeders, but a few may be invasive and/or chemically harmful to corals:

Also, for what it's worth, tunicates are also filter-feeders; some of the colonial tunicate species are invasive enough to smother corals, but if they're isolated, you should be able to contain the spread and prevent any issues. Outside of those invasive species, though, tunicates (both colonial and solitary) are harmless.

I really appreciate your reply, @ISpeakForTheSeas, I kept looking for answers & found some other posts that agree with you.

If you wouldn’t mind answering another question, Are they an indication of anything happening in my tank? Good, Bad? Excess or lack of anything?

 

[ISpeakForTheSeas]

I really appreciate your reply, @ISpeakForTheSeas, I kept looking for answers & found some other posts that agree with you.

If you wouldn’t mind answering another question, Are they an indication of anything happening in my tank? Good, Bad? Excess or lack of anything?

Some people consider them a good sign of a healthy ecosystem in the tank; some might also think they're a sign of high dissolved organics or silicates (neither of which are harmful in most cases).