Re:Trouble With Seahorse

Pete Giwojna

Dear Claire:

I’m sorry to hear that your new female Hippocampus kuda had such a difficult time acclimating to her new aquarium. It’s very difficult to say what may have caused the spasmodic twitching that you describe, but if it was some sort of convulsions due to ammonia poisoning or nitrite toxicity, then the quick dip in methylene blue was an appropriate first aid measure and should have helped the situation. The methylene blue is not at all harmful so administering the dip was good thinking — it could only help the seahorse rather than causing any harm.

Erratic behavior, neurological symptoms, and seizures can also result when a seahorse is suffering from major organ failure, particularly if the liver and/or kidneys are involved. Seahorses have primitive aglomerular (having tubules but no glomeruli) kidneys, whose primary function is to filter waste from the blood (Evans, 1998). The seahorse’s kidneys are also hard at work maintaining its blood and tissues at the proper osmotic concentration at all times (Seahorse Anatomy, 2004). This is necessary because seahorses live in seawater that is four times saltier than their blood and body fluids, and they are constantly losing water via osmosis across their gills, through their skin, and in their urine as a result (Kollman, 1998). Marine fish risk dehydration because salt cannot diffuse into their bodies but water is being continual lost to the concentrated seawater that surrounds them ((Kollman, 1998).

To compensate for this, marine fish drink seawater continuously to replace lost fluids and then excrete the excess salts they have taken in through the kidneys, in their feces, and from their gills (Kollman, 1998). As a result, their kidneys produce a very concentrated, salty urine (Kollman, 1998). Expelling excess salt this way is very energetically demanding and comes at a high metabolic cost because the salts must be pumped out of their bodies against a strong pressure gradient (Kollman, 1998).

Dehydration is always a risk whenever a seahorse is being transferred to a new aquarium with a higher specific gravity or salinity than it is accustomed to, so if your new aquarium has a higher specific gravity than the tank your new female was living in, it is possible that the female H. kuda may have become dehydrated. Dehydration could cause the sort of seizure-like behavior or periodic twitching you reported, Claire, and if so you may want to remove a little of the salt water from the aquarium and replace it with freshwater to lower the specific gravity slightly. That could help the seahorse to recover if it was becoming dehydrated. In severe cases, dehydration can be fatal, but if the female is looking better today that’s a good sign that she is already recovering regardless of whether the problem was dehydration or toxic effects due to elevated ammonia/nitrite levels.

Adding a shallow airstone anchored just beneath the surface of the aquarium would also be a good precaution that may be helpful. That will assure good surface agitation and better oxygenation by promoting efficient gas exchange at the air/water interface, and increasing the dissolved oxygen levels is beneficial in treating ammonia/nitrite poisoning.

Feed the seahorses sparingly the next few days and keep a close eye on the ammonia and nitrite levels in your new aquarium, as discussed below:

Ammonia (NH3/NH4+):
Natural Seawater Value = 0.010 mg/L
Acceptable Range = 0.000 to 0.050 mg/L
Optimum Level = 0 at all times

Ammonia is highly toxic to both fish and invertebrates in even small amounts (> 0.05 mg/L or ppm). Causes of ammonia toxicity include: immature biofilter (new tank syndrome), impairment of the biological filtration due to antibiotics and other medications, overfeeding, overstocking and dead specimens that go undetected (Webber, 2004). Ammonia levels can also rise after the addition of new animals, after a water change, or following a heavy feeding. Any ammonia level above 0.05 mg/L is a cause for concern, and the source must be found and corrected immediately. Be sure to maintain a good schedule of water changes.

Nitrite (N02):
Natural Seawater Value = 0.010 mg/L
Acceptable Range = 0.000 to 0.100 mg/L
Optimum Level = 0 at all times

Nitrite is slightly less poisonous to fishes than ammonia, but deadly to many invertebrates at very small concentrations. Residual levels of nitrite are common in marine aquariums. Levels of 0.05 or less are of little concern in a fish-only aquarium. If the levels are higher than this, the source should be found and corrected immediately. Even trace amounts of nitrite can wreak havoc among the live corals and delicate invertebrates in a reef tank. High levels of nitrite result from the same causes as ammonia.

Best of luck with your new Hippocampus kuda, Claire! Here’s hoping the female makes a quick recovery not in the worse for wear and that the water quality in your new aquarium can handle the increased bioload without any problems.

Pete Giwojna

Post edited by: Pete Giwojna, at: 2009/02/13 19:50

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