Discussion for invertebrate only aquarium

SquidySpecs

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At some point in the future, I would like to set up an aquarium with only invertebrates like snails, crabs, shrimp, brittle stars, and so on. (no fish or corals!) These are in my opinion, some of the most fascinating members of the aquarium hobby and reef ecosystems in general! So naturally I have a few questions about how such an aquarium would be set up? Ideally I would like to keep as wide of a diversity as possible!

1. Has anyone created a similar set up with a focus on invertebrates with no coral, no fish, or neither?

2. What sorts of interesting invertebrates could be kept in a tank without worrying about corals being damaged? Chocolate chip starfish and emerald crabs are examples.

3. What are the best sites to buy cool invertebrates?

4. Are there any incompatible options that aren't commonly talked about? For example, what if anything, would an agressive species like arrow crabs be compatible with?

5. Would any problems not usually encountered in reef aquaria happen in a system without fish or coral?

Thank you for reading!
 

Stomatopods17

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1. I have once, a 20L with an arrow, decorator, and reef lobster. Was kinda boring tbh and ended up trading everything out for a mantis. RN I have a mantis tank (separate build) if that counts and its so interactive I don't get bored of it swimming around or feeding.

2. Snails are typically safe around corals but best to research which ones (especially their growth rate and size), typically they're more of an issue to each other when it comes to threat level. Starfish should be avoided, protoreaster in general is predatory and will lawn mow anything, while the others are very difficult to keep long term due to their diets. Serpant starfish are you best bet, they're harmless scavengers that don't get too big so highly recommend them as long as nothing in the tank will destroy the star. Crabs are opportunist and will pretty much eat whatever is infront of them if they're hungry, I've watched emeralds in my LFS's frag tank pick at the frags and eat them cause theres no rock/sand to even have algae in the tank growing. Sea urchins are way better than starfish, they tend to behave more but best to research which ones are particularly safe and don't get massive (long spines are safe but grow big, fire urchins don't grow as big but like meaty diet and have really bad stings, tuxedos are harmless but will carry around frags so glue anything down.)

3. Any, saltybottom has done me well, reefcleaners i hear great things about, its a matter of you price checking everyone's inventory and what sounds most reasonable to you.

4. Arrows can be kept with pretty much any crustacean, the issue with arrows is they get BIG, I had a female one 8" leg span and it just couldn't fit in my sump and at that size it's game prey becomes better (ate a clown of mine but I think it was already sick). Coral bandeds have a history getting territorial with them likely due to them being big as well. If your heart is set on arrows, a 29L with sally light foots, emeralds, fast shrimp like cleaners, hermits, nassarius snails, should all be fine together while remaining interesting (stuff not hiding out of sight, arrows are in the open and sally light foots are constantly scavenging, you have to have a cover for them they'll crawl out being tide pool crabs)

5. Fish aren't necessary for a reef ecosystem, inverts typically are scavengers and will dirty the water themselves as well as eat the growth on the rock, such as other microrganisms, hitchhikers (arrows love bristleworms), and algae one top of normal feeding. In these more opportunist systems I still sometimes prefer to have a damsel in there to give the upper water column some life, invert only tanks are cool but if you can fit a fish in there why not. There's a damsel with my mantis for the past 6 months.
 

Mr. Mojo Rising

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I have a 5 gallon invert tank, with a coral banded shrimp, and a couple of crabs and snails.

There is no filtration, just a small powerhead and a few rocks. I feed it every day and change the water every 1-2 weeks.

I like it, its easy to maintain, its something different.
 

ISpeakForTheSeas

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2. What sorts of interesting invertebrates could be kept in a tank without worrying about corals being damaged? Chocolate chip starfish and emerald crabs are examples.
Without having to worry about corals, you can pretty much keep any inverts that don't live in corals (like Acropora Crabs or Christmas Tree Worms) - the hard part for this would really just be figuring out which inverts are compatible with each other (for example, you wouldn't want to keep a snail that preys on sea cucumbers or starfish with either of those).

For this question specifically, though, some species include a wide variety of shrimp, Aquilonastra starfish (known as Asterina starfish in the hobby), colonial tunicates and invasive sponges, decorator crabs, meat-eating/omnivorous urchins (such as some pencil urchins), inverts that tend to pick corals up, etc.
 

EricR

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To clarify, are you talking about inverts WITH corals or WITHOUT corals?
*I did inverts only with NO fish and NO corals for about 1 year (I think) but then got confused which way you were leaning by some of the info posted
 
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SquidySpecs

SquidySpecs

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To clarify, are you talking about inverts WITH corals or WITHOUT corals?
*I did inverts only with NO fish and NO corals for about 1 year (I think) but then got confused which way you were leaning by some of the info posted
My intention is to have a tank without corals or fish, I would love to know more about your set up
 
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SquidySpecs

SquidySpecs

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Without having to worry about corals, you can pretty much keep any inverts that don't live in corals (like Acropora Crabs or Christmas Tree Worms) - the hard part for this would really just be figuring out which inverts are compatible with each other (for example, you wouldn't want to keep a snail that preys on sea cucumbers or starfish with either of those).

For this question specifically, though, some species include a wide variety of shrimp, Aquilonastra starfish (known as Asterina starfish in the hobby), colonial tunicates and invasive sponges, decorator crabs, meat-eating/omnivorous urchins (such as some pencil urchins), inverts that tend to pick corals up, etc.
I wasnt aware of any sponges or tunicates that couldn't be kept in tanks with corals, are any of them easy to care for? Also, would having multiple kinds of urchin like pencil, longspine, tuxedo together be possible?
 

EricR

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I stuck with easy and what my kids like so my votes are:
Chocolate chip star
Skunk cleaner shrimp
Conch of some sort (I have tiger sand conch)
Pincushion or tuxedo urchin
Snails of your liking (trochus would be first on my list)
Hermit crabs? (Cool and useful other than going after snails)
***no idea what size tank we're talking about so stock accordingly

*to be clear, I've moved onto corals now so had to donate the CC star and I no longer keep hermits but everything else is still in my current tank
 

TripFamAZ

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I have a mantis shrimp setup and LOVE it. Def consider one if you’re open to what you’re getting. Their personalities are so good!
 

ISpeakForTheSeas

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I wasnt aware of any sponges or tunicates that couldn't be kept in tanks with corals, are any of them easy to care for? Also, would having multiple kinds of urchin like pencil, longspine, tuxedo together be possible?
They're rare and typically highly invasive - so yes, they seem to be easy to care for. The sponges come as occasional hitchhikers, not available for purchase commercially, but a reefer with them in their tank would likely be more than willing to sell them to you. The tunicates can be purchased either from reefers who have them in their tanks or from a source that sells commercially - the source is a coldwater seller, though, so it may take some time to adjust them to tropical temps (yes, the species [which is legitimately invasive] is found in both tropical and coldwater conditions) .

Technically, the tunicates can be kept with corals, they just spread so fast that it's not typically recommended (they'll cover basically whatever rock or glass surface you allow); every now and then, a sponge pops up that outcompetes corals.

Typically, these are either black encrusting sponges - possibly but unconfirmedly Terpios hoshinota - or incredibly invasive white sponges; with the white sponges, only some of the invasive white sponges are actually dangerous to corals, most just grow around the corals' "stems" without actually harming them (this tends to really freak reefers out), but a few will actually either smother the corals or chemically kill them. I've seen a red/orange sponge and a red/pink sponge smother corals too. Photosynthetic plating sponges (which are available commercially) can sometimes be pretty aggressive with spreading and can sometimes shade corals (to the coral's misfortune) as well, but these are considered reef safe.

With the urchins I know some people keep pincushions or tuxedos with rock borers and long spines successfully, so you should be able to keep multiple kinds together without issue, yes. That said, some species of pencil urchin specifically can be pretty predatory omnivores, but I don't know if these would eat other urchins - regardless, if you're going for diversity, I'd be sure to try and pick an herbivorous (or at least not outright predatory) pencil urchin species.
 

Stomatopods17

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I noticed with the hitch hiking sponges they seem to really hate light, they tend to grow in dark areas where you can't see them under the rockwork.

On my 125 I have 3 fixtures, they used to be cheap chinese black boxes and they would burn out and need replacing every other year. On the side of the tank while one of these were burnt out for months I had a huge colony (about base ball size) of sponge growing, since replacing that light this year its all gone, just disintegrated after a few days. I have no clue why adding light suddenly killed it and it only grew when the lights were broken but intentionally running a tank for them is probably not worth it.

Tunicates on the other hand seem to grow fine, I have a massive star polyp colony that at night time reveals a ton of tunicates inbetween the polyps when closed up, they grow everywhere it seems.
 

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