No, sir, I don’t believe that a freshwater dip would be helpful for a seahorse that may have accidentally ingested a foreign object.
The only time freshwater dips are potentially worth the risk are when protozoan parasites or flukes may be infesting the gills of the seahorse.
If you think that could be the case with the seahorse that was breathing rapidly followed by a sort of a hiccup, then be sure to observe all of the necessary safety precautions when performing a freshwater dip, as outlined below:
Here are the instructions for performing a freshwater dip.
A freshwater dip is simply immersing your seahorse in pure, detoxified freshwater that’s been preadjusted to the same temp and pH as the water the seahorse is accustomed to, for a period of at least 10 minutes (Giwojna, Dec. 2003). It doesn’t harm them — seahorses typically tolerate freshwater dips exceptionally well and a 10-minute dip should be perfectly safe. Freshwater dips are effective because marine fish tolerate the immersion in freshwater far better than the external parasites they play host to; the change in osmotic pressure kills or incapacitates such microorganisms within 7-8 minutes (Giwojna, Dec. 2003). A minimum dip, if the fish seems to be doing fine, is therefore 8 minutes. Include some sort of hitching post in the dipping container and shoot for the full 10 minutes with your seahorses (Giwojna, Dec. 2003).
If you will be using tap water for the freshwater dip, be sure to dechlorinate it beforehand. This can be accomplished usually one of the commercial dechlorinators, which typically include sodium thiosulfate and perhaps a chloramine remover as well, or by aerating the tap water for at least 24 hours to dissipate the chlorine (Giwojna, Dec. 2003).
If you dechlorinate the dip water with a sodium thiosulfate product, be sure to use an airstone to aerate it for at least one hour before administering the dip. This is because the sodium thiosulfate depletes the water of oxygen and the dip water must therefore be oxygenated before its suitable for your seahorse(s). Regardless of how you detoxify the freshwater for the dip, it’s important to aerate the water in the dipping container well beforehand to increase the level of dissolved oxygen in the water. Many hobbyists leave the airstone in the dipping container throughout the procedure.
Adjusting the pH of the water in the dipping container so that it matches the pH of the water in the aquarium is a crucial step. Ordinary baking soda (sodium bicarbonate) will suffice for raising the pH of the water. If there is too much of a difference in the pH, there is a possibility the seahorse could go into shock during the dipping procedure. Preadjusting the pH will prevent that from happening. If you will are unsure about your ability to accurately adjust the pH in the dipping container, avoid this procedure altogether or be prepared to monitor the seahorse very carefully or shorten the duration of the tip to no more than about 2 minutes.
Observe the horse closely during the dip. You may see some immediate signs of distress or shock. Sometimes the horse will immediately lie on its side on the bottom. That’s a fairly common reaction — normal and to be expected, rather than a cause for concern, so don’t be alarmed if this happens. Just nudge or tap the seahorse gently with your finger if it lies down on its side. Normally, the seahorse will respond to the slight nudge by righting itself again and calm down for the duration of the dip. However, if it does not respond, stop the treatment.
Most seahorses tolerate the treatment well and experience no problems, but if you see continued signs of distress — twitching, thrashing around etc. — stop the treatment immediately and return the seahorse to normal strength saltwater. How well the seahorses tolerate a freshwater dip can vary from individual to individual and from species to species. Hippocampus barbouri seahorses, for example, often have a low tolerance for freshwater and should either not be dipped or the freshwater dip should be shortened to 1-2 minutes as a safeguard for this species…
After you have completed the dip and returned the seahorses to the aquarium, save the dip water and examine it closely for any sign of parasites. The change in osmotic pressure from saltwater to freshwater will cause ectoparasites to lyse (i.e., swell and burst) or drop off their host after 5-8 minutes, and they will be left behind in the dipping water. Protozoan parasites are microscopic and won’t be visible to the naked eye, but some of the other ectoparasites can be clearly seen. For example, monogenetic trematodes will appear as opaque sesame seeds drifting in the water (Giwojna, Aug. 2003) and nematodes may be visible as tiny hairlike worms 1/16-3/16 of an inch long. Other parasites may appear as tiny dots in the water. Freshwater dips can thus often provide affected seahorses with some immediate relief by ridding them of these irritating pests and can also aid their breathing by flushing out gill parasites.
If you suspect a problem with parasites, the dip should be extended for the full 8 minutes if possible for best results.
If you intend to give more than one seahorse a freshwater dip, I would not dip all of the ponies simultaneously. I would dip them individually so you can keep a close eye on each seahorse throughout the dip and make sure it is tolerating it well. That way, you can use the same dipping container and dipping water for all for seahorses as you dip them in sequence. I like at least a gallon of water in the dipping container, but that depends on what I’m using. If it’s a clean three or five-gallon bucket, I will fill it about half full with freshwater adjusted to the aquarium temperature.
Pete Giwojna, Ocean Rider Tech Support