My best bet is that your seahorses are suffering from the lingering effects of ammonia poisoning and/or nitrite toxicity. This could be due to either a spike in the ammonia level or nitrate level in your seahorse tank or to ammonia exposure while in the shipping bag during transit if the seahorses in question are new arrivals that were shipped to you from long distance.
I would suggest that you check your water quality parameters immediately — especially the ammonia and the nitrite levels — and perform a water change in your seahorse tank to make sure that you are maintaining optimum water quality with zero ammonia and zero nitrite. I would also suggest adding an airstone to the seahorse tank to increase the surface agitation/aeriation and facilitate better gas exchange at the air/water interface to raise the levels of dissolved oxygen in the aquarium. Finally, I would suggest obtaining some Kordon methylene blue from your local fish store in case it is needed to treat this condition.
Ammonia poisoning and nitrite toxicity are completely reversible as long as the seahorse has not been exposed to the unacceptable ammonia/nitrite levels for too long of a period. The best first aid for ammonia poisoning or nitrite toxicity is to immediately transfer the seahorses into clean saltwater with zero ammonia and zero nitrite. If your seahorses are new arrivals that have just been acclimated to the aquarium, you may have already accomplished that, Pattsy, by transferring them out of the polluted water in the shipping bag into the main tank. If so, the usual outcome is that the seahorse makes a full recovery once it has been removed from the polluted shipping water and transferred to the main tank with good water quality and no ammonia or nitrite. But of course you should monitor the ailing seahorse’s condition closely for the next few days in contact me immediately if they show any more symptoms of ammonia poisoning/nitrite toxicity. Here’s what to look for in that regard:
The most obvious symptoms of ammonia poisoning are a loss of equilibrium, hyperexcitability, increased respiration and oxygen uptake, and increased heart rate. At extreme ammonia levels, fish may experience convulsions, coma, and death. Seahorses exposed to less extreme ammonia levels will struggle to breathe. They will be lethargic and exhibit rapid respiration. They may appear disoriented, periodically detaching from their hitching posts only to sink to the bottom.
You mentioned that the seahorse that seems the worst off is just lying on the bottom at times. I have seen seahorses quickly recover with far worse symptoms — lying prone on the bottom unable to right themselves at all for extended periods, blindly bumping into objects on the walls of the aquarium in complete disorientation, and going into actual convulsions, accompanied by severe respiratory distress. By comparison, your seahorse’s symptoms seem relatively mild, so I’m fairly optimistic that it is going to respond well if you have corrected the ammonia/nitrite problem so that he can recover in clean, well aerated saltwater with no ammonia and no nitrite.
As I mentioned, ammonia poisoning is completely reversible providing the seahorses weren’t exposed to toxic levels for too long, and the best first aid you can provide for ammonia poisoning is to immediately transfer the seahorses into clean, well-aerated saltwater with zero ammonia and zero nitrite.
For now, here’s what I’d like you to do, Pattsy:
Leave the aquarium light off today and give your new arrivals as much peace and quiet as possible. It’s all right to observe them from afar, but don’t try to feed them today or do any maintenance on your seahorse tank. I would like you to insert an extra airstone just beneath the surface of the water to increase the surface agitation and promote better oxygenation and efficient gas exchange at the air/water interface, but other than that, just try to provide the newcomers with a relaxing, stress-free environment in the darkened aquarium, and keep a close eye on their breathing rate for any signs of respiratory distress.
Exposure to moderate levels of ammonia and nitrite, or high levels of nitrates, can change the normal hemoglobin in the seahorse’s blood stream to a form (i.e., methhemoglobin) that is no longer able to transport oxygen. If this becomes severe enough, it will leave the affected seahorse starved for oxygen, which makes it very weak and fatigued. As a result, the affected seahorses may detach themselves from their hitching posts periodically and rest on the bottom, unable to exert themselves in their weakened condition. As you can imagine, being deprived of oxygen really wipes them out in terms of loss of energy and stamina. And it also results in respiratory distress, and rapid, labored breathing as they try to oxygenate themselves and compensate for the lack of normal hemoglobin.
One of the properties of methylene blue is that it can reverse this process and convert the methhemoglobin in the red blood cells back into normal hemoglobin, which can then pick up and transport oxygen again as usual. That’s why it is so helpful in relieving shipping stress and treating ammonia exposure and nitrite poisoning. For this reason, you may want to pick up some methylene blue at your local fish store and keep it on hand in case it is ever needed (the Kordon brand of methylene blue is best, in my opinion). So keep a close eye on the seahorse that is lying on the bottom — especially its breathing rate compared to the other seahorse that is now doing well — and be prepared to give it a quick dip in methylene blue as described below.
The usual criteria for determining whether or not methylene blue is needed to help seahorses recover from exposure to high levels of ammonia is their respiration. If the seahorse has labored breathing — huffing or rapid respiration — then methylene blue is called for. Likewise, if the seahorse is experiencing convulsions or it’s behavior otherwise indicates it is suffering from more than temporary disorientation and loss of equilibrium, such as lying prostrate on the bottom, unable to right itself again at all after two or three hours have passed, it may benefit from methylene blue to assist its recovery.
If the seahorse that is repeatedly resting on the bottom is not showing definite signs of improvement and making good progress after a few more hours, then you may want to consider a quick dip in methylene blue. Commonly known as "meth blue" or simply "blue," this is a wonderful medication for reversing the toxic effects of ammonia and nitrite poisoning. Methylene blue transports oxygen and aids breathing. It facilitates oxygen transport, helping fish breathe more easily by converting methemoglobin to hemoglobin — the normal oxygen carrying component of fish blood, thus allowing more oxygen to be carried through the bloodstream. This makes it very useful for treating gill infections, low oxygen levels, or anytime your seahorses are breathing rapidly and experiencing respiratory distress. It is the drug of choice for treating hypoxic emergencies of any kind with your fish. However, methylene blue will destroy nitrifying bacteria so it should be used in a hospital tank or as a brief bath or dip only (if used in an established aquarium, it will impair the biological filtration and the tank may need to be cycled all over again).
Here is some more information that may be helpful if you need to treat with methylene blue after all:
If you can obtain the Kordon brand of Methylene Blue (available at most well-stocked local fish stores), there are instructions for administering it as a very brief, concentrated dip are as follows:
For use as a dip for treatment of fungus or external parasitic protozoans and cyanide poisoning:
(a) Prepare a nonmetallic container of sufficient size to contain the fish to be treated by adding water similar to the original aquarium.
(b) Add 5 teaspoons (24.65 ml) per 3 gallons of water. This produces a concentration of 50 ppm. It is not recommended that the concentration be increased beyond 50 ppm.
(c) Place fishes to be treated in this solution for no longer than 10 seconds.
(d) Return fish to original aquarium.
When you administer such a dip, hold the seahorse in your hand throughout the procedure and time it closely so that the dip does not exceed 10 seconds.
And here are Kordon’s instructions for administering the methylene blue in a hospital tank if longer-term treatment seems appropriate to reverse more severe cases of nitrite poisoning and ammonia toxicity:
As an aid in reversal of nitrite (NO2-) or cyanide (CN-) poisoning of marine and freshwater aquarium fishes:
(a) Remove carbon filter and continue to operate with mechanical filter media throughout the treatment period.
(b) Add 1 teaspoon of 2.303% Methylene Blue per 10 gallons of water. This produces a concentration of 3 ppm. Continue the treatment for 3 to 5 days.
(c) Make a water change as noted and replace the filter carbon at the conclusion of the treatment.
See the following link for more information on treating with Kordon’s Methylene Blue:
Click here: KPD-28 Methylene Blue
If you obtained a brand of methylene blue other than Kordon, just follow the instructions the medication comes with.
One other tip, Pattsy: if you ever need to handle seahorses to administer first aid measures or treat them in a hospital tank, it’s best not to net them when you are manipulating the seahorse:
I do not like to use an aquarium net to transfer or manipulate seahorses, since their delicate fins and snouts can become entangled in the netting all too easily. I much prefer to transfer the seahorses by hand. Simply wet your hand and fingers (to avoid removing any of the seahorse’s protective slime coat) and scoop the seahorses in your hand. Allow them to curl their tail around your fingers and carefully cup their bodies in your hand to support them while you lift them out of the water. When you gently immerse your hand in the destination tank, the seahorse will release its grip and swim away as though nothing out of the ordinary has happened.
Composed of solid muscle and endowed with extraordinary skeletal support, the prehensile tail is amazingly strong. Indeed, large specimens have a grip like an anaconda, and when a 12-inch ingens or abdominalis wraps its tail around your hand and tightens its hold, its vise-like grip is powerful enough to leave you counting your fingers afterwards!
In fact, it can be quite difficult to remove an attached seahorse from its holdfast without injuring it in the process. Never attempt to forcibly detach a seahorse from its hitching post! When it feels threatened, it’s instinct is to clamp down and hold on all the tighter. When you must dislodge a seahorse from its resting place for any reason, it’s best to use the tickle technique instead. Gently tickling the underside of the tail where it’s wrapped around the object will usually induce the seahorse to release its grip (Abbott, 2003). They don’t seem to like that at all, and will quickly let go to move away to another spot. Once they are swimming, they are easy to handle.
Okay, Pattsy, that is my thinking regarding this problem. Check your aquarium parameters to make sure that the levels of ammonia and nitrate in your seahorse tank are at zero, as they should be. If not, perform an immediate water change using freshly mixed saltwater that you have adjusted to the same temperature, pH, and specific gravity as your seahorse tank. Add an airstone to the aquarium to increase the levels of dissolved oxygen but otherwise just keep the tank darkened and give the seahorses plenty of peace and quiet, especially if they are new arrivals that you recently acclimated to the aquarium. In the meantime, purchase some methylene blue from your LFS to have on hand in case it is needed.
Best of luck resolving this problem, Pattsy. Here’s hoping that both of the seahorses are so good as new again.