My experience so far with emeral crabs

JoJosReef

10kW Club member
View Badges
Joined
Sep 27, 2021
Messages
11,693
Reaction score
40,105
Location
Orange County, CA
What state or country do you live in
California
Rating - 0%
0   0   0
To keep bubble algae in check in my IM Nuvo 10g office tank, I've resorted to purchasing emerald crabs, mostly from ReefCleaners. So far, I've gotten 5 from ReefCleaners and 1 from AquaSD.

I am listing a few of my observations in case others have observed similar behaviors.

1. All emeralds introduced so far from ReefCleaners have eaten bubble algae. The one from AquaSD was actually a super bubble algae-eater.
2. In a well-fed reef tank (tank feeding below), all emeralds have gone an intial period of heavy focus on eating bubble algae, and then become "lazy" and prefer to eat leftover fish/coral food or steal food (e.g. from my RFAs). Seems to vary by crab. One of mine became lazy very quickly, within a few days, maybe a week. One went all the way till the bubble algae was 95% gone and then became lazy and didn't return to eating bubble algae even when the 5% remaining algae started to grow back.
3. A couple of emeralds started munching on coral after becoming lazy. Particularly my torch, but one went so far as to take a piece of mantle off a crocea.
4. The one from AquaSD, although the most voracious bubble algae eater, only lasted one day in my tank since it simultaneously wanted to eat zoas, torch polyps and even clam mantle.
5. Some territorial disputes were observed in the 10 gallon, seemingly driven by individual crabs (there were never more than 3 in tank at a time), possibly resulting in death of 3 of the crabs. Currently one has been rehomed, one moved to my Evo and one remaining in my IM 10g.

Conclusion: It would appear that emeral crabs have a limited useful work life in a well-fed tank, ranging from a few days to several weeks. I don't see a way of eradicating the bubble algae, which keeps growing back once they get lazy, except for periodically purchasing new emerald crabs, like once a month or every two months. Has anyone else observed this? Anyone else feel the same?

If interested, here is my tank feeding:
I make a slurry of Reef Nutrition liquid food that I keep in aliquoted tubes in the refrigerator. First recipe was ~250uL each of Mysis Feast, R.O.E., Oyster Feast and 125uL dead Phyto Feast. Current recipe: 250uL each of Oyster Feast, Pac Pods, Arcti Pods, Roti Feast and 150uL Phyto Feast. Each work day, I take out a tube and add 10 medium TDO pellet and ~equal mass of small TDO pellets. This gets fed to a tailspot blenny, a very fat equisite firefish, a spotted nem crab (1 medium pellet target fed), a green porcelain crab (1 medium pellet target fed), 4 RFA anemones (target fed small or medium TDO + slurry) and slurry to the remaining corals (torch, hammer, octospawn, pavona, couple of selected zoas, golden gorgonian, couple of hitchhiker corals). The rest quickly gets picked up by brittle stars, microbrittle stars, various good worms (spaghetti, peanut, NOT bristleworms), sponges, tunicates, etc.
 
What I'm taking away from this is that emerald crabs are inherently lazy, lol. :rolling-on-the-floor-laughing:
Think I heard a collective gasp in your tank. "Can he say that!?"
 
I'm thinking you may want to remove them and then starve them for a while , so far in my 39 I have one and it's done great at removing all algae and other detritus its come across. But then again I do not feed much at all maybe only once or twice a week sometimes less.
 
I'm thinking you may want to remove them and then starve them for a while , so far in my 39 I have one and it's done great at removing all algae and other detritus its come across. But then again I do not feed much at all maybe only once or twice a week sometimes less.
Would work if I had a QT tank maybe. Perhaps can organize a crab share with some of the locals so always in a tank with plenty of bubble algae.

I suppose they don't ever really eradicate it.
 
In my very limited experience. . . small female emerald crabs seem to better tank mates than big males. . . (probably a joke to be made about female and male humans here). . .

Only emerald I ever saw attack a coral was my big male. . . but still now I am afraid to keep them haha
 
naw the only way Ive been able to kill off any pest was usually manual removal and h202 treatments and being very persistent.
 
They are great with algae until the food source starts to dwindle then the nightmare begins. Hopefully you have a different experience
 
They are great with algae until the food source starts to dwindle then the nightmare begins. Hopefully you have a different experience
Hasn't been a nightmare so far. When I catch one messing with a coral, it's easy enough to remove them in a 10g. Donate to a local sump or someone with plenty of bubble algae.

Seems like an unending cycle in a nano though since bubble algae eating herbivorous fish aren't fit for small tanks.
 
Second (third?) the male issue. Mine was GREAT. Voracious clean up crew ... until he wasn't. Then he snacked on Zoas and LPS at his delight, even when target fed nori daily. He got put in time-out for a while, but never went back to eating algae.

I've considered grabbing a female to test the waters (hah), because we love the stupid crabs, but haven't taken the risk yet since I don't have a plan for if/when she doesn't work out.
 
I've seen a similar pattern with emeralds in my 55G, put a few in, they eat a nice bit of bubble algea, then quit. Few more, same thing, clear one patch and quit. Lazy crabs!! :face-with-tears-of-joy:

Now I mostly use a removal tool during water changes. So much for automation!

No issues with them eating corals so far, maybe they just moved on to the hair algea..
 
I've seen a similar pattern with emeralds in my 55G, put a few in, they eat a nice bit of bubble algea, then quit. Few more, same thing, clear one patch and quit. Lazy crabs!! :face-with-tears-of-joy:

Now I mostly use a removal tool during water changes. So much for automation!

No issues with them eating corals so far, maybe they just moved on to the hair algea..
I moved one from my bubble algae tank to my GHA tank, and it seems to be happy there, although still goes straight for the fish food at feeding time.
 

IF YOU HAD TO TAKE A REEFING EXAM, WOULD YOU PASS?

  • Yes!

    Votes: 32 45.7%
  • Not yet, but I have one that I want to buy in mind!

    Votes: 9 12.9%
  • No.

    Votes: 26 37.1%
  • Other (please explain).

    Votes: 3 4.3%
Back
Top