Emerald Crab: Danger to my tank?

[3Poodles&Fish2]

So I am new to this hobby and ran into a problem. Yesterday, I braved to my LFS , water sample in hand to get confirmation that I had completed the great “cycle”. Brand new tank started in mid January my test results were showing that I had, but I saw a sudden spike again in ammonia so I waited a week after adding nitrifying bacteria. My LFS ran their tests and I about fainted when the manager came up and said that my water was perfect - even my pH was perfect and that was often an issue in our area.

I wanted a clean up crew because my substrate (sand) is a mess and I’ve noticed a film of “fuzz” on my live rock. I had pictures I showed them and they agreed. I got the following;

* 25 Blue Legged Hermits
* 3 Emerald Crabs
* 1 Cleaner Shrimp

Upon looking more at the photos the guy helping me asked the specifics again on my tank and I reiterated

60 gallon cube
20 gallon Sump system w/ 2 sock filters and 1 pound carbon
Sicce Syncra 3.0 SDC (800 pgh)
Sicce heater
Water temp 78*f

He recommended some fish specifically a foxface or tang. So I got both because they had some small ones and were quite a bargain. My 2 year old niece was with me and was enthralled with the “Nemo” fish. And the guy said that it was a safe idea. So I got that too. I was concerned about the bio load (probably from too much reading in these forums) and the sales guy asked me to take out the mollies and return them to be safe. Full disclosure and transparency, in addition to the CUC I added;

Blue hippo tang (about the size of a silver dollar)
Yellow Tang (same size as blue one)
2 ocellarus “Nemo’s” (pair)
1 spotted foxface (about 3” big)

So yesterday, I brought it all home, acclimated it all to the tank, released it in the tank, and woke up this morning and the cleaner shrimp is not moving looking half dead on the tippy top of the highest rock very near where it was released. I called my LFS who had me bring back the carcass/dead body along with a water sample. They detected slight elevations in ammonia, but nitrite, phosphates nitrates, and Everything else was in order. They gave me a new cleaner shrimp this one was double the size the one I originally purchased. I went through the same routine brought it home acclimated it into the tank. We went out to dinner and I came home and noticed that the shrimp wasn’t acting right. I noticed that it was pinned into the live rock by two Emerald crabs. That shrimp is dead, and I have photos and video of the crabs, eating and pinching at the shrimp. The one crab appears to be more (most) aggressive by dragging the shrimp up the rocks away from the other 2 crabs and all the hermits (that just follow). Currently the crab has the shrimp up under a rock high off the floor.

Tomorrow I call LFS again. Meanwhile, I’m worried because I really want one of those pistol shrimp/watchman goby pairs…

The fish are all doing great! I ran my water tests and everything was what it was except ammonia that was “perfect” (0.03) yesterday and registering 2.3 tonight. I did a 20 percent water change and now ammonia is 0.09.

Remember I’m new. I’ll figure out how to post a photo next. The photos from my phone are too big…

 

[CBonito]

Emeralds are a tossup. Sometimes they will never touch anything, and other times emerald crabs you didn't know you even have will get caught eating a 200 dollar acro colony in the dark and end you know how that ends...most people seem to believe they are fine and while they could totally be right, my experiences with them were always negative.

 

[Lavey29]

First you bought fish that should not be in your small tank. 60g is 45g with rocks. Adding that many fish to a new tank probably caused an ammonia spike. The crabs were just eating an already dead shrimp. Please do some research and educate yourself to the hobby and note the minimum tank size for the fish you have.

 

[littlefoxx]

I have a large emerald (half dollar size) and he doesnt mess with my fish or shrimp. Also have a few emeralds in my other tank and they dont do that either, leads me to think the shrimp died. The combo of fish the store suggested is not good advice for your tank size nor age of your tank with the exception of the clown fish. Too much CUC also for how new the tank is with no fish and no feedings before they were put in. The foxface will outgrow that tank in maybe 2 months, they grow fast. Got one under an inch about 6-7 months ago for my big tank and he is already 5 or so inches, the biggest fish in the tank. I suggest taking the foxface back, they really need a big tank right away since they grow fast. Also in case the store didnt tell you, foxface has venomous spines. Hurts like heck. Be careful handling/moving things in the tank with them

 

[The_Paradox]

Two of my favorite tanks are cubes. That being said, you really need to stock them as if there were half the volume they actually are unless you really know what you are doing. Ie look for fish that can go in a 30 gallon tank in your case. You can add a few more than you could in a true thirty but nothing that really requires more space if that makes sense.

 

[His Coral Highness]

Haha those are not 60 gallon fish…

 

[Katrina71]

Your lfs did not give you good advice. Be saving for a much bigger tank.

 

[vetteguy53081]

So I am new to this hobby and ran into a problem. Yesterday, I braved to my LFS , water sample in hand to get confirmation that I had completed the great “cycle”. Brand new tank started in mid January my test results were showing that I had, but I saw a sudden spike again in ammonia so I waited a week after adding nitrifying bacteria. My LFS ran their tests and I about fainted when the manager came up and said that my water was perfect - even my pH was perfect and that was often an issue in our area.

I wanted a clean up crew because my substrate (sand) is a mess and I’ve noticed a film of “fuzz” on my live rock. I had pictures I showed them and they agreed. I got the following;

* 25 Blue Legged Hermits
* 3 Emerald Crabs
* 1 Cleaner Shrimp

Upon looking more at the photos the guy helping me asked the specifics again on my tank and I reiterated

60 gallon cube
20 gallon Sump system w/ 2 sock filters and 1 pound carbon
Sicce Syncra 3.0 SDC (800 pgh)
Sicce heater
Water temp 78*f

He recommended some fish specifically a foxface or tang. So I got both because they had some small ones and were quite a bargain. My 2 year old niece was with me and was enthralled with the “Nemo” fish. And the guy said that it was a safe idea. So I got that too. I was concerned about the bio load (probably from too much reading in these forums) and the sales guy asked me to take out the mollies and return them to be safe. Full disclosure and transparency, in addition to the CUC I added;

Blue hippo tang (about the size of a silver dollar)
Yellow Tang (same size as blue one)
2 ocellarus “Nemo’s” (pair)
1 spotted foxface (about 3” big)

So yesterday, I brought it all home, acclimated it all to the tank, released it in the tank, and woke up this morning and the cleaner shrimp is not moving looking half dead on the tippy top of the highest rock very near where it was released. I called my LFS who had me bring back the carcass/dead body along with a water sample. They detected slight elevations in ammonia, but nitrite, phosphates nitrates, and Everything else was in order. They gave me a new cleaner shrimp this one was double the size the one I originally purchased. I went through the same routine brought it home acclimated it into the tank. We went out to dinner and I came home and noticed that the shrimp wasn’t acting right. I noticed that it was pinned into the live rock by two Emerald crabs. That shrimp is dead, and I have photos and video of the crabs, eating and pinching at the shrimp. The one crab appears to be more (most) aggressive by dragging the shrimp up the rocks away from the other 2 crabs and all the hermits (that just follow). Currently the crab has the shrimp up under a rock high off the floor.

Tomorrow I call LFS again. Meanwhile, I’m worried because I really want one of those pistol shrimp/watchman goby pairs…

The fish are all doing great! I ran my water tests and everything was what it was except ammonia that was “perfect” (0.03) yesterday and registering 2.3 tonight. I did a 20 percent water change and now ammonia is 0.09.

Remember I’m new. I’ll figure out how to post a photo next. The photos from my phone are too big…

With exception of clowns, the other fish are NOT good first fish and was the tank actually cycled? If so, how did you cycle and how long>
Additionally, an emerald crab especially male can be destructive and go after coral. I trust a politician more than I do an emerald crab.
Test water again in the morning as , if you test right after water change, you will likely get a false reading.
Crabs are scavengers and will eat dead fish, shrimp and uneaten food

 

[3Poodles&Fish2]

With exception of clowns, the other fish are NOT good first fish and was the tank actually cycled? If so, how did you cycle and how long>
Additionally, an emerald crab especially male can be destructive and go after coral. I trust a politician more than I do an emerald crab.
Test water again in the morning as , if you test right after water change, you will likely get a false reading.
Crabs are scavengers and will eat dead fish, shrimp and uneaten food

I started a cycle 6 weeks ago with MicroBacter Start XLM and 25 saltwater Mollies. I have tested everyday and notated the levels. There was a clear spike in Ammonia and NItrites/NItrates - I shared this info with LFS.

 

[3Poodles&Fish2]

Two of my favorite tanks are cubes. That being said, you really need to stock them as if there were half the volume they actually are unless you really know what you are doing. Ie look for fish that can go in a 30 gallon tank in your case. You can add a few more than you could in a true thirty but nothing that really requires more space if that makes sense.

I realize that the Foxface and Tangs are temporary - LFS suggested them for a few months to help clean up the algae from the Mollies that helped cycle the tank. Ultimately, my plan or vision is a coral tank with a few fish. I knew that a 60g tank is limiting what fish I can have...

 

[3Poodles&Fish2]

I have a large emerald (half dollar size) and he doesnt mess with my fish or shrimp. Also have a few emeralds in my other tank and they dont do that either, leads me to think the shrimp died. The combo of fish the store suggested is not good advice for your tank size nor age of your tank with the exception of the clown fish. Too much CUC also for how new the tank is with no fish and no feedings before they were put in. The foxface will outgrow that tank in maybe 2 months, they grow fast. Got one under an inch about 6-7 months ago for my big tank and he is already 5 or so inches, the biggest fish in the tank. I suggest taking the foxface back, they really need a big tank right away since they grow fast. Also in case the store didnt tell you, foxface has venomous spines. Hurts like heck. Be careful handling/moving things in the tank with them

Yes, the did educate me on the spines and proper handling.

 

[3Poodles&Fish2]

Thanks all for the feedback and advise! It is greatly appreciated as I continue to learn this hobby.

 

[The_Paradox]

I realize that the Foxface and Tangs are temporary - LFS suggested them for a few months to help clean up the algae from the Mollies that helped cycle the tank. Ultimately, my plan or vision is a coral tank with a few fish. I knew that a 60g tank is limiting what fish I can have...

Urchins would have been a much better suggestion if you have coralline along with green algae problems.

 

[MoshJosh]

As noted above, the emeralds are opportunistic and probably were eating things that had already died or were sufficiently weakened. Also as noted above, emeralds can be a toss up as far as the destruction they can cause. . . I personally like them and have a few in my tank, but they are always a risk.

Yeah your tank is too small for some of the fish you got, sounds like your LFS kinda did you dirty on that. People definitely keep fish temporarily, but even small tangs will benefits from lots of swimming room. . . Plus trying to catch a tang out of an established tank with corals in it sounds like a nightmare to me haha

Some alternative creatures for algae control might be: lawnmower Blenny, “reef safe” urchins, and pitho crabs (a new favorite of mine).

As always try and do tons of research before making tank additions and when in doubt ask Reef2Reef haha

 

[PotatoPig]

For future reference - barring a few niche cases, snails tend to make better CUC than most crabs. There’s very little crabs will eat that they won’t, they’re more economical, and there are far fewer issues with them eating corals/critters.

This isn’t to say don’t add crabs, they’re interesting additions to a tank and can add color and character, but perhaps not as the core of a CUC.

 

[Starbuxxx]

Emerald Crab - I never had an issue with them but I overfeed to keep my inverts fed.

Livestock - There is way too much going on for a 60 gallon. 25 hermits, 25 mollies, And the tangs, man. Slow down. take your time. this much livestock in a 60 gallon with throw off parameters and things will start dying.

 

[kevgib67]

Emerald crabs eat mostly algae although they are omnivores. I had them in my tanks for most of the over 18 years of reefing and never seen them hunt down a living thing. Come to think of it, I’ve never seen them go after anything dead however the hermits and nassarius snails make quick work of things.

 

[exnisstech]

25 mollies to cycle a tank. That's pretty aggressive. I do fishless cycles but if I did use fish it would be a single damsel. Ghost feeding will accomplish the same thing.
After reading everything the LFS recommended for your size tank I would probably look for another store.

 

[twentyleagues]

I have never seen an emerald crab go after a healthy fish or shrimp maybe a shrimp for territory but not to eat. I have seen them mess with corals especially lps same with shrimp. I learned long ago snails are a much better choice for cuc. All crabs are opportunistic and none are strict herbivores.

 

[jda]

IME, only a hungry emerald crab will go and try and catch anything or eat a coral. Who know if they ate at your LFS. If you expect them to eat poop, then they might eat corals or try and catch a shrimp or fish - so would you or I.

Edit: not all algae is nutritious, tasty or otherwise going to be food for crabs and fish. Some things that people want them to eat are not algae at all and can hurt them like dinos, diatoms and matting bacteria.