Yes, I suspect you’re on the right track. Most likely the overfeeding initially has resulted in an ammonia spike due to the excess nutrient loading in the aquarium. If so, a 49-gallon aquarium with lots of live rock should adjust quickly to the increased bioload. It sounds like you are well aware of the situation and have already corrected the feeding problem that resulted in the excess Mysis being scattered throughout the tank. You did a good job of cleaning up as much of the uneaten Mysis as possible, and I expect that the ammonia levels will be returning to normal sooner rather than later now that you have taken the appropriate steps to prevent a recurrence of the problem.
I would feed your new Mustangs sparingly for the next few days while you monitor the ammonia levels and make sure they continue to drop back down to zero. Keep a close eye on the seahorses for any signs of ammonia poisoning in the meantime, and be prepared to make another water change or to treat the seahorses with methylene blue, if necessary. Here’s what to look out for, Sean:
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.
Since your Mustangs are not showing any of the symptoms mentioned above, it appears that you have detected the problem in time to prevent any harmful effects. Just be on the lookout for any signs of the respiratory distress that is often a symptom of lesser ammonia levels and be ready to treat the seahorses with methylene blue if they are having difficulty breathing.
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.
If your Mustangs begin to develop respiratory problems due to the ammonia spike, 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, Sean: 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.
Best of luck getting your ammonia levels back down to zero, Sean! In your case, I asked that the problem will resolve itself over the next few days without any need for any sort of treatment.