I’m sorry to hear about the trouble you’re shy seahorse got into. Very occasionally seahorses may try to squeeze through an opening that as too tight and gets stuck. This sometimes happens when they are hunting copepods and amphipods among the rockwork. They will become real contortionists trying to get at Gammarus amphipods that are hiding underneath rocks and in the nooks and crannies of the rockwork.
But most of the time when a seahorse gets wedged tightly amidst the rocks, it is a seahorse that has been weakened (perhaps by illness or malnutrition) and was swept into a tight spot by water currents, and was unable to free itself or fight the current in its weakened condition. You might want to rearrange the rockwork where the incident occurred and/or adjust the water currents in that area to prevent a recurrence of this problem.
You did great to discover the seahorse’s predicament, free him, and give them some prompt first aid. But you need to be a little cautious when treating seahorses with Melafix. Melaleuca tree oil (the active ingredient in Melafix) can sometimes be a risky treatment for seahorses due to the potential risk of asphyxiation, as discussed below.
My main concern with Maleluca tree oil is that it may impair the breathing of seahorses under certain circumstances for a couple of reasons. First of all, it seems to stimulate excess mucous production, and may cause the gills to be coated with a layer of slime. Secondly, it reportedly causes a drop in oxygen (O2) levels during treatment.
The drop in O2 levels is definitely a cause for concern, particularly if excess mucous production is impairing respiration by causing the gills to be coated in slime at the same time. If a thin film of this oil covers the surface of the aquarium, that could interfere with efficient gas exchange at the air/water interface, resulting in a drop in O2 levels and a build up of CO2.
One property of the Maleluca tree oil is that it dramatically reduces the surface tension of the water, causing protein skimmers to go nuts and overflow with copious amounts of wet foam. Skimmers usually need to be shut off during treatment as a result, so maybe that reduces the oxygenation in the aquarium further.
In short, it appears Melafix is contraindicated in cases where the affected seahorse is experiencing respiratory problems. I would say it is never advisable to use Melafix when seahorses are huffing, exhibiting labored breathing, or showing any signs of respiratory distress. And it would certainly be a sensible precaution to increase the aeration, surface agitation, and circulation in your hospital tank when treating with this product. Consider adding an extra airstone or two to be safe.
So if you notice a change in the seahorse’s breathing during the Melafix treatments — any signs of respiratory distress — I would discontinue the Melafix immediately and remove the medication from the water ASAP. Start up your protein skimmer, resume filtration with fresh activated carbon, and perform a water change right away.
The primary risk with a mechanical injury like this that leaves the seahorse scraped up is secondary infection that takes hold at the site of the injury. For this reason, it would be a good idea to administer a broad spectrum antibiotic such as kanamycin or neomycin to help stave off such infections.
At the very least, you may want to consider treating the scrapes with BioBandage, Don. This is a combination of neomycin, a vitamin complex, and unique polymers that form a sort of "biological bandage" that binds the medications to the wound, thus helping to prevent infection and promote rapid healing. It can be obtained online from the following vendor:
Aside from preventing secondary infections, you should be concentrating on getting some nutritious food into your shy stallion while he is undergoing treatment in your hospital tank. Try tempting him with some choice live foods. Adult brine shrimp that have been enriched (i.e., gutloaded) and disinfected would be a good choice as would small ghost shrimp.
If you cannot obtain any live foods locally, then I would suggest that you try some of the live feeder shrimp from Seawater Express instead. They provide bite-sized white shrimp (Penaeus vannamei) in batches of anywhere from 50 to 1000 each. They are hardy, easy-to-keep and disease free. I recommend getting the smallest of the "Snicking Shrimp" they offer in order to fatten up your ailing female a bit:
Seawater Express Inc.
Organic Shrimp Farm / Hatchery
In short, I would suggest that you go to your LFS and obtain a good broad-spectrum antibiotic that’s effective against gram-negative bacteria, pick up some Bio-Bandage, and get some choice live foods to fatten up the seahorse well he is being treated and help him regain his strength. Keep him in the hospital tank until the regimen of antibiotics has been completed and stay on top of the water quality with daily water changes (redosing the antibiotic after the water changes in accordance with the instructions for the antibiotics).
Best of luck healing your stallion that literally got himself stuck between a rock and a hard place, Don! Here’s hoping that he is good as new before you know it.