Christopher:
Species distinction is one of the most perplexing facets of seahorses.  Genealogy is difficult to ascertain from outward appearances alone, and often times, seahorses are labeled incorrectly as a result of coloration alone.  Hippocampus kuda has become a sort of "catch-all" distinction when the species is unknown or the labeler is inexperienced with seahorses.  Oddly enough, true H. kuda are somewhat a rarity in the hobby in the majority of the United States, although almost every marine fish store sells them!

There are a variety of elements to look for when trying to determine a seahorse's species.  The crown, or coronet, is a good place to start.  Crown shapes vary widely, but can be key in distinguishing say, H. erectus from H. kuda.  For instance, H. erectus has a more prominent and bony crown compared to H. kuda's lower profile, smoother crown.  Other physical characteristics such as the dorso-ventral depth of the body, number of body and/or tail rings, snout length, and notable markings can also be helpful in determining species.

For details and specifics, you can refer to the "Quick ID Guide for the Hobby's Most Common Seahorses" on the syngnathid.org site at http://www.syngnathid.org.

Question:
I've read that lighting is not an important factor in seahorse keeping.  I have a question about aquarium lighting and gas bubbles in seahorses.  My 30-gallon tank had about 1.5 watts of light per gallon originally.  After I installed Power Compact fluorescents my wattage jumped to 4 watts per gallon.  The temp remains at a steady 76°F in the tank and circulation appears sufficient.  After installing the PC lights I noticed air bubbles appearing on the substrate and the walls of the tank.  I'm assuming that the lighting is causing the algae and probably other micro-life to respire and create gas bubbles.  I may be wrong about this, but the bubbles seem to be linked to the lighting, and if so, would the same lighting intensity cause similar gas bubbles in the skin of a seahorse?  My thinking is that the skin of seahorses must be contaminated to some extent with algae and these algae probably exchange gases.  - Darrell

Christopher:
This is a very interesting line of thought, Darrell, and an excellent question.  Those bubbles you are seeing on the glass and rockwork are indeed cause by the increased oxygen output of the algal matter in the tank.  Photosynthesis consumes CO₂ and releases O₂ and increasing the intensity of the lighting cause a substantial increase in photosynthetic activity.  The increase in O₂ levels in the tank result in bubbles collecting on the glass and rockwork.

Now, as for the relationship between subcutaneous gas bubbles and increased photo intensity, although, as Carol points out earlier in the column, seahorses do use algae for camouflage, this relationship is purely external.  Were it more akin to the relationship between corals and their symbiotic zooxanthellae, this increased algal respiration may account for the subcutaneous gas bubbles that sometimes occur in seahorses.

Let me digress slightly from the question here to address the actual cause and treatment of this malady.  Subcutaneous gas bubbles are usually a symptom of declining water quality and/or bacterial infection.  Finding and remedying the water chemistry problem(s) can generally clear them up.  However, if the bubbles persist, you may need to lance them by sterilizing a pin and puncturing the skin parallel to the body of the fish so as not to injure the fish.  Subsequent to the lancing of the bubbles, the use of a topical disinfectant such as betadine, povodine, or even Neosporin will help the wounds heal.  In acute cases, it may become necessary to treat with the appropriate antibiotics to eradicate the offending bacteria and finally clear up the bubbles.

Question:
When considering tankmates is the activity level of the tankmate as big an issue as competition for food? Will fish that are too active stress the horses?  - Leslie

Christopher:
Choosing tankmates for your seahorses is something that should take careful consideration.  For me, personally, I, first, try to think of the natural environment of my horses as much as possible, and stock the corral with tankmates that the horses would normally interact with in the wild.  However, this can lead to an aesthetically limited aquarium, so, the next step is to find other organisms that you like.  Sadly, many marine fish do not make suitable tankmates because they will outcompete seahorses for food, or may attack the horses.  Activity level is not so much a factor as aggressiveness, though.  I keep a medium-sized dragon wrasse (Novaculichthys taeniourus) with my horses and he is in constant motion except at night.  The addition of this fish almost 2 years ago has had little noticeable effect on the horses eating and breeding habits.  Granted, this fish is a fierce food-competitor, so I actually feed him first and let him eat his fill before focusing on feeding the herd.

As long as you choose tankmates that will not prey on or harass the seahorses, you should have no problems at all.