I have one Alpheus immaculatus, as well as several other Pistol Shrimps (8 in total = 5x Alpheus bellulus and 3 x Alpheus randalli) along with several Shrimp Gobies (6 in total = 2x Cryptocentrus cinctus, 2x Stonogobiops nematodes and 2x Stonogobiops yasha). There is also 3 Pearly/Yellow headed Jawfish (Opistognathus aurifrons). All of the shrimps and gobies have paired in different combinations, excepting the Alpheus immaculatus, which has remained solitary at all times. The area this shrimp lives in is the only area in my tank where the Gobies have not made any attempt to inhabit! In fact, had a Jawfish killed by the Alpheus immaculatus when it attempted to construct a burrow in its area. From my observations I believe that Alpheus immaculatus does not pair with any commonly kept Gobies and it will not tolerate and kill any fish that enters its territory. It is also growing quite quickly and is now the largest Pistol Shrimp in the tank (from 1" to 2 1/2" in 6 months), I am currently hoping to trap it and remove it from the system with a X-Terminator Mantis Shrimp Trap I have ordered from the USA.
Thanks for the interesting email, and what seems like a unique aquarium environment! As you may know, I am not a scientist, but do have the following thoughts: You seem very sure the shrimp is Alpheus immaculatus, and not another closely related species, such as Alpheus armatus, A. roquensis, or A. polystictus (this one gets to about 2 inches in body length). I mention this since no photo was included in your email, and the fact you mention its size, which is, if for body length, larger than what can be expected for A. immaculatus, (usually about 1.5 inch).
If you have included the claws in the length, then let me assume you're correct about the species, and go from there. First, the species is from the Tropical Western Atlantic/Caribbean. Basically, it associates with anemones, such as the Corkscrew Anemone Bartholomea annulata, not fish species. However, if not A. immaculatus, and possibly that of the above mentioned other species, i.e., A. armatus and A. roquensis, they will not associate with Bartholomea annulata, and prefer other species anemones such as Bartholomea lucida and Bellactis ilkalyseae. But if A. polystictus, it also associates with the Corkscrew Anemone.
Therefore, its reluctance to share its space with others in the aquarium is understandable. And even if tempted to add one of these anemones to its area, be forewarned this is a stinging anemone/fish eater often thought of as a 'pest' anemone, and rarely cherished by aquarists. But if you do decide to place a small corkscrew anemone in its area, the shrimp will move close to its column or dig a burrow next to it, as this 'is' their preferred location as the stinging tentacles of the anemone provide it with peace of mind from predators. And would think it simply was protecting its area from 'invading' species when it killed the jawfish, who was do doubt looking for a place to dig a new home.
Hope this has been helpful,
Thank you very much for your reply, as it was very interesting and useful. My tank is mainly for SPS corals, but I am fascinated by creatures that live either on or in the sand bed, and with this in mind I supported some reef plates on a few small pieces of live rock when aquascaping my tank and then put the sand bed over these so there was plenty of places underneath for Shrimps, Gobies and Jawfish to safely excavate burrows and therefore reducing the possibility of dead spots forming in the sand bed. On top of the reef plates I have three towers constructed from Tonga type branching live rock on which SPS have been placed.
By the way I forgot to mention in my last email I also have two Randall's Gobies Amblyeleotris randalli (unfortunately not a pair), so it makes a total of 8 gobies not 6 as I previously stated, along with the 8 shrimps (not counting the Alpheus immaculatus). The Yellow Watchmen Cryptocentrus cinctus are a true pair and stay together the majority of time, the other gobies have not paired. The gobies are mainly peaceful as there is no aggression from the larger Amblyeleotris and Cryptocentrus species towards the smaller Stonigobious gobies and they will sit in their burrows less than 2 inches apart at times. Between the Amblyeleotris and Cryptocentrus gobies there seems a mutual respect, where should they come too close to each other they will open their mouths wide as a threat, but there is no physical contact between the two species and the intruder will back away to a reasonable distance. The only actual aggression that results in contact is between the two Amblyeleotris randalli's when very occasionally (approx once a month) the larger Randall's will evict the other Randall's and move in with the previous occupants shrimp. The confrontation results in the nipping of the smaller fishes dorsal fin although no real damage is done that hasn't healed within a day. The smaller fish is very submissive and doesn't suffer much inconvenience, and it will then move in with the shrimp that has been abandoned by the larger fish. All of the shrimps seem to tolerate each other and do not intrude on the others territory, although despite the high number of shrimp none have paired.
Just this weekend I found a Alpheus ochrostriatus, which I'm planning to add to my tank, and I know this is a suitable Goby partner for it, so it will be interesting to see which gobies it will associate with and if it has any different habits to my existing shrimps. I also may have an option on a Alpheus rubromaculatus, which I know is usually associated with the Whitecapped goby Lotilia graciliosa, however these gobies are possibly (as available) too small and are definitely too expensive for my tank. Would you know if this shrimp will bond with other goby species and is it happy with a mixed coral rubble sand bed or does it prefer and come from mud flats?
Let me first say you are to be highly praised for your attention to the environment in your aquarium!
Amblyeleotris guttata (also Amblyeleotris ogasawarensis Amblyeleotris steinitzi, and Amblyeleotris wheeleri) are probably good partners for the soon to be added Alpheus ochrostriatus. However A. ochrostriatus is also known to associate with Cryptocentrus species and this should probably make an interesting addition to your now quite fascinating and interesting aquarium setup!
As for Alpheus rubromaculatus, which prefer a sandy, lagoon bottom/reef slope location, I believe you're correct as to its goby association, and do not know of other associates. But as an experiment in your aquarium, it should be interesting watching!