An article by Dan Underwood of Seahorse Source regarding Freshwater Dips
Occasionally a seahorse hobbyist runs into a situation where a freshwater (FW) dip is indicated. A FW Dip can be used as both a therapeutic and a diagnostic tool. As a therapeutic tool it can help rid the seahorse of ectoparasites on the body, in the oral cavity, as well as in the gills. As a diagnostic tool, observation during the dip will give you a good idea if there is a parasitic load or not. It can also be done prophylactically on new arrivals from suspect sources, on wild caught (WC) specimens or when a tank mate has had known parasitic load.
How a Freshwater Dip Works
Seahorses are complex, multi cell organisms whereas many parasites, such as protozoans, are
simple single cell organisms. The difference in osmolarity between the saltwater (SW) and FW is
the magic key to the dip. The hypotonic environment of the FW creates an osmotic imbalance to
the protozoan. This causes water to move into the protozoan to balance it which then causes
them to rupture or burst. Some larger more complex parasites in the mesozoan or metazoan class
may not burst as quickly as the protozoans, but the change in osmostic pressure shocks them
causing them to detach and in many cases, perish. Seahorses being a much larger more complex
organism can handle the osmotic change for a much longer time and are able to compensate for
the changes during the time it takes for a FW Dip. Basically, the FW is not harmful to the seahorse, but can be deadly to the parasites.
When to use a Freshwater Dip
A Freshwater Dip can be used as a diagnostic tool, to determine whether the problem with seahorses is related to parasites, or as the beginning of a treatment plan if you know there is a problem. There are several instances where one may want to consider a FW Dip, including:
- On new arrivals that are from suspect sources or with WC specimens
- When seahorses are scratching
- On specimens that have rapid respirations when there is no other obvious cause
- As an initial treatment for Weak Snick
- If you see little organisms on the seahorse
- As a prophylactic measure when a tank mate has a known parasitic load
Using the dip as a “diagnostic” tool describes doing the dip when you see a seahorse scratching or breathing heavily for no reason. If there are other seahorses in the tank that are not having the same issues, a Freshwater Dip can help you figure out what is wrong with the one having the issues. “Scratching” is something that seahorses just do sometimes. If you see them “scratching” their back on a display item, there’s no reason to worry. But, if you see them using their tail to try to scratch their gills constantly (literally like a dog with fleas), then it’s time to try a freshwater dip to determine if the problem is ciliates or parasites. After doing the dip, you will know if the problem is related to ciliates or parasites because you will possibly see little specimens in the dip water, and see a big difference in the seahorse – he won’t scratch!
Finally, a Freshwater Dip can be used as therapeutic tool if your seahorse develops “Weak Snick” – a condition in which the seahorse tries to eat, but can’t seem to snick up the food. Click here to learn more about Weak Snick if your seahorse is having trouble eating. And use a freshwater dip to clear the seahorse’s gills, body and oral cavity of any ectoparasites that may be causing the problem. In many cases, a FW dip might solve the problem, but it will definitely help you determine what the problem actually is.
When to NOT use a Freshwater Dip
You should never do a dip on a seahorse that has an open wound or might have a bacterial infection. A seahorse with an open wound is already injured and he or she is experiencing a situation the same as if one of us humans were deeply cut or injured. The osmotic shock that a seahorse can usually handle with no problem….becomes a problem when an injury has occurred. When a seahorse has a bacterial infection, he or she needs a different type of treatment and the FW dip will just cause them more stress in their already weakened state. Click here to learn more about how to deal with a seahorse that has a possible bacterial infection.
Materials Needed for a Freshwater Dip
- Container. A clean container to hold the FW and Seahorse. This can be anything from a small
tank such as a 2.5 or 5 gallon tank, a large jar, or a bucket. The container does need to be clean
and needs to be able to hold enough water to cover the Seahorse in an upright position. My
personal preference is to use a 2 gallon glass cookie jar from Walmart. This holds enough water
and after the dip I can swirl the water around and concentrate the dropping to examine under a
microscope. It is also very easy to sterilize post dip. - Fresh Water. We prefer to use Reverse Osmosis (R/O) or Distilled Water. Tap water can
sometimes be used but it needs to dechlorinated. - FW pH Test Kit.
- Buffer. This is used to adjust the pH of the water to match the tank.
- Thermometer. We prefer infrared thermometers that don’t require touching the water or
needing to be sterilized between tanks. This is used to verify the FW and the tank water are at the
same temperature. - Airline & Air Pump. The FW will need to be aerated and you should have a bubbler running
during the dip to keep the oxygen saturation up. - Hitching post. Some consider this optional. This can be very simple. Just something for the
Seahorse to hitch to should it desire to. In many cases they won’t use it but some do. - Timer, clock or stopwatch for timing the procedure.
- Mentor or other experienced person. If you are really worried about the procedure or if this is
the first time, nice to have someone handy, even it is over the phone to give encouragement,
support and answer any questions. - Optional
- Dissecting Microscope or other magnifier to examine what comes off the Seahorse.
Preparing for the Freshwater Dip
The first step is to pick out and setup a container for the FW Dip. Any container that holds
enough water to cover the seahorse can be deployed, but it should a CLEAN container. Our favorite
container for this purpose is a large Cookie Jar from Walmart. They have them in 1 and 2 gallon
sizes and the lid is not used. We like this container because it is cheap, round, being glass very
easy to clean, doesn’t have any seems and we can easily view the animal during the
procedure. But, a bucket or 2.5 or 5 gallon tank can be used as well.
Next, you should consider placement of the container for observation and proximity to the display tank. You want
the container somewhat close to the display tank so you don’t have to carry the seahorse very far
to it and can easily and quickly return the seahorse back to the display tank or hospital/quarantine
tank.
Then, you will need to add freshwater – R/O or distill water is ideal – but tap water can be used if it
doesn’t have any chlorine or chloramines. If either of these are present in your water, it needs to be neutralized prior to the FW Dip using a product Sachem Prime. The temperature of the water needs to be same as the tank or no more than 1 degree different. It can be adjusted prior to adding to the vessel or afterwards depending upon your method of adjusting the temperature. A heater can be used temporarily to raise the temperature or ice in a ziplock bag can be used to lower the temperature. But the important point is to make sure the temperature of the FW dip water is the same as the temperature of the tank to make the seahorse more comfortable.
An airline will need to be added to the FW and should be run for a few minutes prior to adding the
seahorse, to bring up the oxygen (O2) saturation. R/O, distilled or tap water can often have a very low 02 saturation level. We prefer to use a rigid airline without an air stone but an air stone may be used if desired.
You will also need to test the pH of the display tank where the seahorse is and the FW. If the pH
is different (the FW is almost always lower than the tank), you will need to add buffer to match the pH of the FW to the tank the seahorse was taken from.
A hitching post should be added to the container. The seahorse will feel less stress and be more comfortable with a hitch. The hitch can be anything that is not too large. It should be clean and either easily sterilized or disposable. A plastic plant, artificial coral or any object that is clean and easy for the seahorse to hitch to can be used. Many people even use zip ties to provide this hitch for the seahorse.
Performing the Freshwater Dip
Gently place the seahorse in the FW container. Begin the timing of the procedure and observing
the seahorse. You will want the FW Dip to last a minimum of 8 minutes and if there is a reaction
to the dip, then you should continue for at least 12 minutes or up to 15 minutes.
The seahorse is likely to react in one of 3 ways after placement in the FW Dip.
1. First it could move about normally or hitch.
2. Second it could play possum and lay on the bottom.
3. Lastly, it could begin to thrash about.
Watching for what happens is how to use the FW dip as a diagnostic tool! It is also not uncommon to see what appears to be particles in the water shooting away from the seahorse. This would be little organisms reacting to the FW Dip. But, even if you don’t see them, continue the dip!
If the seahorse acts normal throughout the first 8 minutes and doesn’t do any thrashing or show other signs of irritability, the seahorse probably doesn’t have much of a parasitic load. In this case, you should discontinue the FW Dip at this point and move the seahorse back to the display tank or Hospital/Quarantine tank.
If the seahorse should just lay on the bottom, look to make sure the seahorse is continuing to breathe. This is a defensive move on the part of the seahorse to make other’s think it is dead. In some cases it may stay there or may get up and move about. Often, if you give it a nudge it will get up. Either way watch for signs of thrashing or irritability.
In some cases, the seahorse will begin to thrash about or become highly irritable. This may happen quickly or can take a few minutes to develop. Their reaction may range from very mild to very active. It can be very disturbing to one not familiar with this process. This is a sign that the FW Dip is doing what it is supposed to be doing. A person’s natural instinct is to remove the seahorse, but the best thing to do is to go the full 12 to 15 minutes. What is happening is that the little organisms (parasites) are trying to burrow deeper to get away from the FW and the osmotic shock. This is quite uncomfortable and irritating to the seahorse, but actually helping him or her. Once you have gone the full
12 to 15 minutes, remove the seahorse and place back in the Display tank or Hospital/Quarantine tank.
If the original symptom or complaint was rapid breathing or weak snick, you may have to wait up to 24 hours to re-evaluate. This is to allow for healing and a reduction of edema within the tissues from the parasites. Some cases may warrant further treatment such as a Formalin Dip or long term Formalin Bath. We don’t recommend multiple FW Dips done in succession. We have seen fungal issues appear when too many FW Dips are done to close together. Generally it is better to consider another form of treatment, versus doing multiple FW dips.
Another consideration when you have positive results of parasites from the FW Dip is to go ahead and treat any other seahorses that were in the same tank. Odds are if they aren’t showing any symptoms, they may soon start to. The procedure remains the same for the other seahorses.
After the Freshwater Dip
After the FW Dip is done, many like to examine what came off the seahorse. If you used a round
container or if you pour the FW into a clean round container such as a bucket, you swirl the
water around so that it begins to spin. The contents in the water becomes concentrated in the
center of the spin. A sampling can be removed with an eye dropper, small syringe or even a
turkey baster. You can then look at the contents under a microscope or other strong
magnification. You will likely be surprised at how much stuff you find. It will be hard to identify
everything due to the bursting from osmotic pressure, but you will likely find it very interesting.
Further Reading
Fish Diseases and Disorders, Volume 1: Protozoan and Metazoan Infections, 2nd Edition. Edited
by P.T.K. Woo, University of Guelph, Canada 2006
Marine Ornamental Species, Collection, Culture & Conservation, Edited by James C. Cato and
Christopher L. Brown, Iowa State Press 2003
Fish Diseases, Diagnosis and Treatment, Second Edition, Edward J. Noga, Wiley-Blackwell, 2
edition, 2010
Fish Parasites, Pathobiology and Protection, Patrick T. K. Woo & Kurt Buchmann, CAB
International, 2012
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