Shrimp, Snails and Dwarf hermit crabs coexisting well

[Corucia]

I’m case there group is curious, I wanted to share my latest dwarf hermit crab experience as I reintroduced the zebra variant into some of my tanks.

I previously had six of these in my smallest setup (3 gallons) and had pretty good luck with them. Of the six, I lost one roughly each year for the first four jeers. However, one survived for over eight years and I still have one going strong and now that is +10 years old.

I introduce the new fellows into my larger tanks -- 6 and 7 gallons -- last month and they are doing great. Of the dozen, I’ve only had one death (on the second day) which was probably related to acclimating to brackish vs full salinity (I drip acclimated them for around five hours). All the others appear healthy and vibrant. They are very busy beavers, constantly grazing on algae, cyanobacteria and detritus.

While I know there has been some concern over the impact these crabs might on the shrimp and snails (inc aggressive behavior and predation), to date the crabs seem totally disinterested in them, other than swapping in and out of some of the vacant snail shells. T This was my experience in my 3 gallon tank although I suspect the crabs did dine on juvenile snails as that population ultimately dwindled as the older fellows died off (I have one large elderly snail left in that tank).

Finally, a curious observation. When I initially introduced the crabs to the tanks, the shrimp definitely took notice and in one tank in particular the majority of them hid for the better part of two weeks. However over the ensuing weeks they all came out and now seem to be totally integrated with the crabs, to the point where I’ve seen several will ride one the crabs backs grazing on the algae on their shells.

Some pics below of them coalescing my seven gallon tank. I’ll keep the group updated on how each tank evolves.

[OpaeOasis]

From what I've read, the major concern with dwarf hermit crab and opae ula cohabitation is the requirements for the crab: assuming your snail population can support them, that would be a great loophole around having to add supplemental food. The addition of extra food for the crabs, which require much more than the shrimp, is the reason many struggle to keep them alive (in a typical setup, they would starve, and overfeeding to support a larger bioload can overwhelm any system). I wouldn't worry about predation, the opae ula are very fine-tuned towards disturbances to a degree where I would deem it nearly impossible for them to be caught. Your system must be very well balanced!

[Corucia]

Thanks for the note OpaeOasis. I read similar things before introducing the dwarf crabs to my 3 gallon tank a decade ago. My personal experience with them runs totally counter to what’s been posted elsewhere.

First, the species is herbivorous. Any predation that occurred in my first tank (which I never witnessed live) would have been among the very juvenile snails. The mature snails all were unimpacted by their introduction. Also, as the tank has reproduced shrimp year in and out, there doesn’t seem to be any noticeable predation of the Opae, fry or adults.

Regarding the food requirements, I never changed the feeding cycle for the three gallon tank after I introduced the crabs. I just continued to put in a modest about of crushed pellets every two weeks. Mind you, the crabs would race to grab the food when placed in the tank but in the two week interim, they were perfectly happy just grazing on the algae, detritus, etc. There didn’t appear to be any starvation issues as the first one that passed away was in the tank for about two years.

Plus the fact that two of the six made it +8 years (and one is still going at +10 years) based on this feeding cycle gives me confidence that in a well established tank with vibrant algae there is more than ample food resources to keep a small crab population healthy, regardless of what is written and no need for extra feeding above what is normal for the Opae.

I suspect that some of the posted thoughts on this topic could be based on speculation/conjecture vs. actual first hand experience but I’d love to hear of others experience keeping dwarf hermit crabs in Opae environments. Clearly more work and study should be conducted on the topic to form definitive views on the the husbandry of these dwarf crustaceans.

[OpaeOasis]

Always great to see the boundaries expanded for the hobby! I myself managed to achieve "the impossible"- I acclimated freshwater algae to grow in my setup, it's done great and thrived for over a year (unlike any mario moss balls!)
There's always potential to experiment and discover unlikely scenarios like this, it just takes someone brave (and possibly with some screws loose ) to make it happen, keep it up!

[Corucia]

Indeed OpaeOasis. It’s both fun snd intellectually rewarding seeing what can be achieved in these environments. For reference here is my +10 year old crab grazing on Algae right next to the shrimp. They totally coexist without any friction.

Per my other post, I’ve been able to cultivate Batophora occidentalis successfully in my largest tank after failing to get it to take in thee of my other tanks (and it failed the first time in this one as well). Maybe we can swap some of our algae to see if we can get each to take in our respective environments.

[Vorteil]

@opaeoasis
what freshwater algae were you able to grow? Pics?

I just read your other post on the algae

[OpaeOasis]

I have read that post, I didn't realize it was yours
That Batophora occidentalis is definitely gonna change the entire hobby once the ideal parameters and shipping method are discovered. With the die-off and sporing life cycle, it may be unfit for smaller systems (plus it seems to multiply rapidly), but I would definitely be a "guinea pig" for it once it becomes available on the site! I think these methods would work: shipping water from the tank (with hopes of spore/gamete introduction), or a whole plant attached to a pebble (which would likely be damaged through shipping, but also reproduce in the long run). My unusual algae was discovered along a park trail in very shallow water (it didn't go above my ankles), attached to tiny rocks. I've seen larger specimens in larger water bodies, so I assume it was limited by the environment. Similarly, despite the reputation of cladophora in freshwater aquaria, it has never grown fast enough to be a concern. I believe it doesn't receive enough nutrients to overtake everything, but I do find tiny new growths in my tank (plus new plants from fallen pieces, I was a bit rough while transferring it a couple times). While I wish it was intact, any small pieces seem happy to grow elsewhere. Here is the large original plant being scrubbed by the shrimp, they love it!

The other pieces are on the other side of the tank, there's some tiny new plants at the rock peak as well (they only settle where light is highest, I discovered that in my previous setup). They grow much slower than simple divisions, so that seems to be the best propagation method.

[Corucia]

Quick update. The zebra dwarf hermit crabs have all acclimated well and grazing actively on the algae in the tanks. They also periodically congregate together, which is pretty funny to watch.