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Discussion Starter · #1 ·
I apologize that I have to skip the formal introduction, as this is my first post on this forum I've been following for so long.

Recently I set up a new system only using spare parts. Old powerheads, bad lightning and no intention of keeping either fish or corals.

5 months into this little 30g system, some weird, black bulges has started growing everywhere. I intentionally let it flourish when I first saw it on a rock, because I'm keeping this small tank for the sole purpose of experimenting. It grows primarily on sand. Some sparse vegetation on rocks. It doesn't look or act like any other potential bubble algae I've seen before.

The algae(?) looks squishy and bubbly, but it's actually completely solid and it feels like squeezing soft cheese. It doesn't break easily either. Inside they look like a grapefruit that has had it's skin peeled.

I know it's a sort of vague description, but I hope the pictures can make it a little clearer what I'm talking about.

In addition to know what it is, I'm curious what might be causing it. What sort of nutrients it feeds off of. Also, what might feed on it.
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Have a nice day!
Moeshi
 

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Ive seen that in a LFS's display fuge. My assumption from how I remember it before was dead/dying cyano. A thin film with almost a velvety texture appearance wise.
 

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Discussion Starter · #3 ·
Ive seen that in a LFS's display fuge. My assumption from how I remember it before was dead/dying cyano. A thin film with almost a velvety texture appearance wise.
I can't imagine it being cyano, as it required low flow. On the contrary I think it's more related to the opposite. The powerheads have a combined power of 660gp/h. The tank is only 30g. Not even copepods or snails can hold on to the glass in the areas with the highest flow - let alone the sand. The liverock in the center is without a doubt the area that gets the least flow. Both heads are pointed at the front glass, and the strange growth is just below on the sand, whilst there is close to nothing on the rocks.

Also, is it possible for bacteria to be solid as I described? It doesn't come off easily and it takes an entire patch of sand with it, when I lift up a piece.

Nitrates are 0
Nitrites are 0
Salinity is 1.024
pH is 8.1
I have no account of anything else.

I have no idea how to distinguish it as a sponge, if that's the case. The two turbos and one super tiny hermit crab that lives in the tank, as well as asterina stars, strombus hitchhikers and amphipods, doesn't seem to mind it. They don't eat it, but they aren't exactly afraid of touching it, although they avoid crawling on it most of the time.

I don't feed the system.
 

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The Fang Blenny
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First off, welcome to TRT! :wavey:

Hmm, I would have to agree with Bill that it looks a lot like cyano. It looks filmy and is often located on the sandbed, but it's mostly red/brown... I've learned that wherever an algae grows is usually the location of the organic source that is fueling the fire. Phosphate is a prime fuel source, and it can be present in your rock and sand, or the water and food that gets put into the tank. You may wanna try a Hanna phosphate test and see where those levels are.

You said you don't feed, but what type of water are you topping/mixing with? What type of filtration are you using? What does your maintenance schedule look like? The lighting and flow could also be the cause...

With 660gph to 30g tank capacity, that's only 22x turnover rate by your powerheads. That's pretty low (usually the rates found in a softy coral tank). But since you aren't keeping any corals, probably not a big deal unless you wanna get rid of this stuff.

An encrusting sponge or tunicate will have several siphon openings, and you should be able to see them. There is a black encrusting tunicate that I have seen before, but I've never heard of them encrusting sand. These sensitive (and sometimes needy) inverts are seen in older "mature" systems that have the nutrients in the water column needed to sustain them. If you want, I can snag a pic of my yellow encrusting sponge colony that has spread throughout my 180.

I love the idea of having an empty tank just to experiment. I hope it's been a rewarding experience so far.

Keep on reading! Hope you find your answer :)
 

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Welcome to TRT. Looks like cyano to me. It can be red or black. I think this is part of your silicate cycle. Your tank is going through the uglies right now, because of the low bioload. Mine happened in a few months. Some take weeks. Most tanks don't fully mature for a year or more. you just have to wait it out and increase your cleaning regiment until it's gone. 660gph is not a lot of flow for a 30G, but it's enough. Your algae is nothing I haven't seen before in my 5 years of reef keeping. So just relax and increase your water changes.
Why not add any fish?

https://www.reefcleaners.org/nuisance-algae-id-guide
 

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Could it be black bubble algae? It is hard to tell in the picture but it looks almost bubbly.
 

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I'm going with sponge. They eat bacteria that they filter through their system. This one covers about 20% of my tank and has been growing for years. They come in all colors and I see black ones on the reef all the time.

 

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Sponge usually won't grow back in a week or even a few days. I think it takes a little bit longer for sponge to grow. clean the sand and see if it comes back within a few days.
 

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Discussion Starter · #9 ·
Thanks for all the great inputs. I greatly appreciate it!

To avoid too much quoting I will try and answer everything from the top.

The growth doesn't feel slimy to the touch. In addition to that, it's so tough that I have to use a scalpel to cut through the center of it because I can't tear it using my fingers. I can squeeze it thin as a dime however. What appears to be a film on the sandbed is actually solid in shape. Its almost as it grows up from underneath the sand. When I remove a larger chunk it takes at least a month for growth to re-appear.
There might be some resemblance to holes in some of the larger structures. I will try and get a good picture of that.

Phosphates might very well be a factor here. I only do water changes every once in a while, and when I do I often use tapwater instead of my RO water.
As for filtration I use an external canister with a little over 10x the volume pr. hour.
I know this is insufficient, as the feather-duster worms are experiencing a golden era at the moment. They are ALL over the place. They are growing huge too! Bigger than I thought these small critters could even get.
This is partially on purpose since I don't feed the system what-so-ever.

The growth of coralline algae in the tank is very slow. I believe this is due to the poor lightning quality. I use an old expired florescent tube from my DT, which is several years old. However, the tank receives one-two hours of direct sunlight in the morning around 8 am. This doesn't seem to affect the growth or destitution of neither the coralline or the growth in question.

As for why I don't want to keep any fish in the system, it's because the main purpose of the tank is to observe things that are otherwise impossible with predators around. I've had the pleasure of watching all sorts of spawning and behavior of all the thousands of critters that live hidden in a normal tank. Also, I would hate to have a fish living under sub-optimal conditions like these.

I will snap some pictures of a desiccated specimen as soon as possible. I will also test for phosphates.

Once again thanks for all the help. You guys are amazing.
 

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Discussion Starter · #10 ·
First of all, I apologize for the semi-necro.

Real life has kept me from the hobby for some time now, and the growth in questions has been the least of my worries since then.
I thought I would post one final update should somebody, someday search this topic, looking for answers.

After removing it all by force, it slowly grew back after a months time. It wasn't quite as dense or as large, and since then it has been a steady decline. First it turned pale, then white, and finally it started to dissolve and break apart. Today a few pale specimens remain here and there, but all growth has come to a complete halt.

Whatever it was feeding on it took 5 months to deplete it, and now it's dying.


I want to thank you all for the great advice and suggestions I received.


Happy reefing,
Moeshi
 
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