Dear Lisa & Andrew:
Please do keep working to line up a source of the Diamox one way or another — you are going to need the acetazolamide in order to clear up the subcutaneous emphysema (a.k.a. tail bubbles or external gas bubble disease), and the sooner you begin administering the Diamox, the better the outcome is likely to be.
I agree that transferring a small sand sifting goby to your seahorse tank will probably be fine, and that there shouldn’t be any aggression towards the seahorses. But you can never be 100% certain about such matters.
When reading up on compatible tankmates for seahorses you are bound to come across some conflicting information and contrary advice on this topic. Personal opinions on the subject will vary depending on the individual hobbyist’s experiences when keeping seahorses in a community tank, and what works well in one aquarium isn’t always successful in another setup.
When discussing compatible tankmates for seahorses, Lisa, it’s important to remember that one can only speak in generalities. There are no unbreakable rules, no sure things, no absolute guarantees. For instance, most hobbyists will tell you that small scooter blennies make great tankmates for seahorses and 9 times out of 10 they’re right. But every once in a while, you will hear horror stories from hobbyists about how their scooter blenny coexisted peacefully with their seahorses for several months and then suddenly went "rouge" overnight for no apparent reason and turned on the seahorses, inflicting serious damage before it could be captured and removed.
Does that mean that we should cross scooter blennies off our list of compatible tankmates for seahorses? Nope — it just means that we must be aware that individuals within a species sometimes vary in their behavior and respond differently than you would expect, so there are exceptions to every rule. It’s fair to say that scooter blennies generally make wonderful companions for seahorses, but there’s always a small chance you might get Satan reincarnated in the form of a scooter blenny. There’s no guarantee that adorable scooter you picked out at your LFS because of his amusing antics and puppy-dog personality won’t turn out to be the blenny from hell once you release him in your seahorse setup.
Your sand sifting goby falls in the same category as a scooter blenny, Lisa. The vast majority of the time, we would expect the goby to get along great with seahorses, but there is always a correspondingly small chance that things could go horribly wrong at some point.
Likewise, micro-hermit crabs are generally entertaining additions to an aquarium that do a great job as scavengers and get along great with seahorses, but over the years, I’ve had a few seahorses that were confirmed crab killers. These particular ponies were persistent hermit crab predators that specialized in plucking the hermits out of their shells and attacking their soft, unprotected abdomens, and they honed their skullduggery to a fine art. They were experts at extricating the crabs and would eat only their fleshy abdomens and discard the rest. Mind you, that was only a few individuals out of a great many Hippocampines, but I could never keep hermit crabs in the same tank with those specific seahorses.
It’s the smallest hermit crabs that are at greatest risk, of course, but this behavior sometimes becomes habitual. So if my experience is any guide, crab killing could become a bad habit for the seahorse that is doing the stalking and you’ll have to watch that particular pony around hermit crabs from now on. Once they have discovered how to go about it, a seahorse may develop a taste for hermit hinders and consider them to be a regular part of its menu henceforth.
On the other hand, sometimes it’s the micro-hermits that are the troublemakers. Most of the time, they coexist perfectly well with their fellow janitors in the cleanup crew. But I’ve had more than a few tiny hermits with a taste for escargot that persecuted snails mercilessly. These cold-blooded little assassins would kill the snails in order to appropriate their shells. Once they had dined on the former occupant, they would take up residence in their victim’s cleaned-out shell! It soon became clear that these killer crabs were driven not by hunger, but by the need for a new domicile. Once I realized they were house-hunting, I found I could curb their depredations but providing an assortment of small, empty seashells for the hermits to use. Colorful Nerite shells are ideal for this.
Since you are going to have few snails in your seahorse tank, you can certainly consider adding a number of seahorse-safe hermit crabs to act as aquarium janitors. Hermits that fit the bill include Dwarf Blue-legs (Clibanarius tricolor), Left-handed (Calcinus laevimanus), Mexican Red Legged Hermits (Clibanarius digueti) and above all, Scarlet Reef hermit crabs (Paguristes cadenati), which are my personal favorites.
The Scarlet Reef Hermit Crab (Paguristes cadenati) is a colorful micro-hermit that’s a harmless herbivore. So cannibalism isn’t a concern at all for these fellows, nor are they likely to develop a taste for escargot. As hermits go, most of the time the Scarlet Reefs are perfect little gentleman and attractive to boot. I even use them in my dwarf seahorse tanks. Best of all, they eat all kinds of algae, including nuisance algae such as red, green and brown slimes, as well as green hair algae.
If you’re going to have any hermits, stick with species like the above, which are known as micro hermits because they start out tiny and stay small. Avoid Anomura species of hermit crabs no matter how small they are, however, because they will kill Astraea snails to obtain their shells.
The sand sifting crabs offered by saltwaterfish.com would also be a good choice for your seahorse tank, Lisa, as discussed below:
"The Sand Sifting Crab is a small round-bodied gray crab with small digging appendages, but no true claws. These little crabs bury themselves into the sand. When feeding they’ll leave their forebody out of the sand, using two small "scoops" to catch food. These crabs are peaceful and can be kept in groups. The Sand Sifting Crab will not eat any beneficial creatures in the sand bed; they are filter feeders. They are also a great feeder food for larger fish."
I would also recommend including some nassarius snails in your cleanup crew. They burrow in the sand and will therefore serve as sand sifters, and they are good scavengers for a seahorse tank because they prefer meaty leftovers such as uneaten frozen Mysis.
However, I would not transfer your sand-sifting starfish to your seahorse tank even temporarily, Lisa. Sand sifting starfish are fairly delicate and can be somewhat difficult to keep alive. They do best in large aquaria (55 gallons and up) with a deep live sand beds that have been well-established and therefore have built up a large population of meiofauna. There just isn’t going to be an enough fodder for a sand sifting starfish to thrive in a small seahorse tank with a shallow sand bed, particularly a newly established tank. I wouldn’t consider adding a sand sifting starfish to any aquarium until it had been up and running for at least six months or a year.
If you can refresh my memory regarding how big your seahorse tank is and how deep the sand substrate is in the seahorse setup, I can provide you with better recommendations regarding the cleanup crew. Do you have live rock in your seahorse tank, Lisa?
Best of luck lining up some Diamox for your stallion and cleaning up the sand bed, one way or another, Lisa and Andrew!