What do you think these bright blue patches growing on my rock are?

[Finatic]

I've been keeping freshwater planted aquariums for over a decade and finally decided to make the dive into saltwater/corals a few weeks ago. My tank is a Fluval Evo 13.5 with stock lighting, stock pump, and a small 240gph Hydor koralia nano powerhead. Intake chamber has been converted into a small refugium with chaeto from my LFS and I'm running an ATO with fresh rodi. The tank has been up and running for exactly 3 weeks as of today. Rock is two medium sized pieces of caribsea liferock, and 1 box of caribsea fragzone rock. At around two weeks in, I noticed these bright blue patches forming on my rock all across the tank. It first started on the frag pieces, but is now starting to form on the two bigger pieces as well. The owner of my LFS says that it looks like sponge growth to him, which is what I'm hoping for, especially being that it's a gorgeous blue color. I wanted to get some additional opinions on what others think this might be. I would add more pictures, but pretty much all of the other patches I'm seeing are on the purple epoxy which makes it hard to see the color, this picture has some white in the background so it's easier to see the color. What do y'all think? I've read that coralline algae can sometimes be blue, but it seems like my tank is too new to have this much growth if that were the case. Whatever it is, I love it, I just hope that it's not something that will be a nuisance when I start adding corals.

 

[T-J]

Wait...tank is 3 weeks old and you already have frags in there?
Also, is that reddish/purplish color cyano or diatoms? Or is that the color of the rock?

 

[Mr. Mojo Rising]

I suspect it has something to do with the lighting, I've never heard of anything blue. Did you take the pic with only white lights on? Anyway, your rocks are going to go through a whole lot of color changes in the next few months.

 

[Finatic]

Wait...tank is 3 weeks old and you already have frags in there?
Also, is that reddish/purplish color cyano or diatoms? Or is that the color of the rock?

No, no frags yet, that's just what caribsea calls these small little life rocks. They are caribsea "fragzone" life rocks. So I'm just calling them frag rocks to keep it shorter. These rocks are where I first started noticing the bright blue patches about a week ago, but now I'm seeing them on the two large pieces of caribsea life rock as well. I just put them in there to fill the tank out a little bit, and I probably will use them to place some corals that I don't want to take over my bigger rocks in the future. Or I might just scrap them completely for bigger pieces, haven't really decided yet. The reddish purple is just the epoxy/paint/whatever you want to call it that the liferock comes with. They came all together in a bag, so the white spots you see are where the rocks have scraped together and the paint has come off, or at least that's what I'm assuming. They were dry when I put them in the tank 3 weeks ago. The only new color on the piece pictured is the bright blue patch there. I did have a diatom bloom about 1 week ago, but after adding a small clean up crew, it has mostly dissipated although there are still some light patches of it on some of the rocks and sand but the piece pictured here doesn't seem to have any diatom that I can see on it.

 

[Finatic]

I suspect it has something to do with the lighting, I've never heard of anything blue. Did you take the pic with only white lights on? Anyway, your rocks are going to go through a whole lot of color changes in the next few months.

I was wondering that myself, so I took one out of the water and shined my phone light on it. The blue became a little bit less bright, but still visibly blue. So I don't think it's entirely a light thing, something is definitely growing here, I just don't know what the heck it is. lol. I'm skeptical that it's sponge, it just seems like my tank should be too new for that, but then again I'm out my element here so I truly have no clue. lol. Regardless, I'm here for the changes, can't wait to see it morph! I'm thinking about waiting until month two to start adding any corals. Would you say that's a good time frame to wait?

 

[Reefkeepers Archive]

Definitely not coraline, that stuff takes months to years to grow

 

[Finatic]

Definitely not coraline, that stuff takes months to years to grow

Yeah, I figured it would be way too soon for that. I was thinking maybe some kind of cyanobacteria? But most of the pictures I've seen of marine cyano looks more reddish/purple than blue. This is like BRIGHT blue. It's a gorgeous color, I just cant figure out what it is.

 

[Reefkeepers Archive]

Yeah, I figured it would be way too soon for that. I was thinking maybe some kind of cyanobacteria? But most of the pictures I've seen of marine cyano looks more reddish/purple than blue. This is like BRIGHT blue. It's a gorgeous color, I just cant figure out what it is.

New tanks usually have a different strain of cyanno, one that is bright green/blue, could also be entrusting sponge but if it's more of a film then it's probably cyanno

 

[Finatic]

I suspect it has something to do with the lighting, I've never heard of anything blue. Did you take the pic with only white lights on? Anyway, your rocks are going to go through a whole lot of color changes in the next few months.

New tanks usually have a different strain of cyanno, one that is bright green/blue, could also be entrusting sponge but if it's more of a film then it's probably cyanno

I just did a google image search for encrusting blue sponge, and I think that's it. It doesn't have a film whatsoever, it's very uniform. It's hard to say with the patches being pretty small still, but it looks almost identical to this dark blue encrusting mat sponge. Color and texture seem to match up! From the very little that I've read on it just not, it seems to be a good thing. I hope you're right, because this stuff is gorgeous! Man, how do I ever go back to freshwater now? This is too cool!

 

[X-37B]

If it feels rubbery its a sponge

 

[Finatic]

If it feels rubbery its a sponge

I don't think I have any patches that are quite big enough to really get a good feel of the texture yet, but when I do, I'll give it a good fingering and see!

 

[X-37B]

I don't think I have any patches that are quite big enough to really get a good feel of the texture yet, but when I do, I'll give it a good fingering and see!

Here is a rock in my 45 with blue sponge although it looks purple its actually blue.
Also if you use a soft toothbrush on it and it comes off its not a sponge.

 

[Finatic]

Here is a rock in my 45 with blue sponge although it looks purple its actually blue.
Also if you use a soft toothbrush on it and it comes off its not a sponge.

That is so freaking cool. I just used an old soft toothbrush on the patch that was pictured and it didn't budge one bit. So that's a good sign. Can sponges be a problem for corals or is that something I shouldn't really worry about? Doesn't seem like they are causing you any trouble there.

 

[Harold999]

I welcome everything on my rocks, except hairalgae and bryopsis.

 

[bshonesy]

Here is a rock in my 45 with blue sponge although it looks purple its actually blue.
Also if you use a soft toothbrush on it and it comes off its not a sponge.

That’s so cool that you have this and it’s thriving like that. Sometimes sponges don’t do that well. Did you get it as a frag, or is this a Florida rock or something? In a previous tank I did one of those Florida rocks and it had red encrusting sponge on it that used to love.

 

[Finatic]

I welcome everything on my rocks, except hairalgae and bryopsis.

I'm all too familiar with hair algae, but I've never heard of bryopsis until now. Just read about it a little bit and now I'm scared. Thanks! lol

 

[X-37B]

That’s so cool that you have this and it’s thriving like that. Sometimes sponges don’t do that well. Did you get it as a frag, or is this a Florida rock or something? In a previous tank I did one of those Florida rocks and it had red encrusting sponge on it that used to love.

I got it an lfs. Tank breakdown rock for $40. I have a large amount of an orange sponge attatched to my 7 year old frogspawn. Most tanks have different types of sponge. You usually dont see them as most grow under the rocks.

 

[ISpeakForTheSeas]

Can sponges be a problem for corals or is that something I shouldn't really worry about? Doesn't seem like they are causing you any trouble there

It depends on the sponge, but most are completely harmless. There are a few that are bad news for corals, but you can usually figure out that they’re troublesome pretty quickly.