I’m very sorry to hear about the problems you had with internal GBS, but I think you’re on the right track. I suspect that low-level supersaturation of the carrier gas for the ozone is what triggered this episode of gas bubble syndrome (GBS)). Reducing the ozone to its former level is a wise precaution and may help prevent any further problems with gas supersaturation.
Gas bubble syndrome (GBS) is a mysterious, widely misunderstood affliction that can take on many different incarnations. As you know, piper, gas bubble syndrome is believed to be caused by gas emboli forming within the tissue of heavily vascularized portions of the seahorse’s anatomy — the placenta-like brood pouch of males, the eye, the muscular prehensile tail — and it can take several different forms depending on where the bubbles or emboli occur. When it occurs in the brood pouch of the male, chronic pouch emphysema or bloated pouch results, leading to positive buoyancy, which is by far the most common form of GBS. When it occurs in the capillary network behind the eye (choroid rete), Exopthalmus or Popeye results, and the eye(s) can become enormously swollen. When it affects the capillary network of the gas bladder (the rete mirabile), hyperinflation of the swimbladder occurs, resulting in positive buoyancy. When it affects the tail or snout, external gas bubbles (i.e., subcutaneous emphysema) form just beneath the skin and look like raised blisters. When intravascular emboli occur deep within the tissue and occlude blood flow, generalized edema results in the affected area. Or extravascular emboli may cause gas to build up within the coelom, often resulting in positive buoyancy and swelling or bloating of the abdominal cavity (internal GBS), as appears to be the case with your Hippocampus kuda and H. barbouri seahorses, piper.
Different parts of the body can thus be affected depending on how the
initial gas emboli or micronuclei form, grow and spread. During an
episode of GBS, bubbles may initially form in the blood
(intravascular) or outside the blood (extravascular). Either way,
once formed, a number of different critical insults are possible.
Intravascular bubbles may stop in closed circulatory vessels and
induce ischemia, blood sludging, edema, chemistry degradations, or
mechanical nerve deformation. Circulating gas emboli may occlude the
arterial flow or leave the circulation to lodge in tissue sites as
extravasular bubbles. Extravascular bubbles may remain locally in
tissue sites, assimilating gas by diffusion from adjacent
supersaturated tissue and growing until a nerve ending is deformed or
circulation in nearby capillaries and vessels is restricted. Or,
extravascular bubbles might enter the arterial or venous flows, at
which point they become intravascular bubbles. Extravascular bubbles
can thus become intravascular bubbles, and vice versa, via diffusion
and perfusion. This is important because it means that under certain
conditions extravascular seed bubbles or micronuclei can enter the
bloodstream and migrate from their birth site to other critical areas
as intravascular bubbles. If untreated, the gas bubbles worsen and
the condition is fatal.
Gas bubble syndrome is not a disease that seahorses contract after being exposed to a pathogen of some sort, but they will often develop the condition when kept in a system that exposes them to gas supersaturation, insufficient water depth, stress, inadequate water circulation, a bacteria-laden substrate or other environmental factors conducive to the formation of gas emboli. In other words, it is an environmental disease, triggered by certain conditions within the aquarium itself. In my experience, the environmental triggers that are most often associated with GBS are as follows:
1) Insufficient depth (aquaria that are less than 20 inches deep are very susceptible to GBS, and the taller the aquarium is, the more resistant it will be to GBS).
2) Gas supersaturation of the aquarium water, which can lead directly to the formation of gas emboli within the blood and tissues of seahorses.
3) Changes in the seahorse’s blood chemistry (i.e., acidosis). Anything that tends to acidify the blood of the seahorses can result in GBS, including stress, low levels of dissolved oxygen and/or high levels of CO2, and low pH in the aquarium water, among other factors.
In your case, piper, I suspect low-level gas supersaturation is the culprit, and the increased flow of ozone appears to be what triggered the supersaturation. If so, then reducing the ozone may have corrected the situation.
In general, it sounds like your reef system is very well designed. The sump is wonderful for increasing the overall water volume of the system and allowing for more efficient filtration. Installing a sulfur denitrator to keep the nitrates as low as possible is also a very nice addition. You have a top quality protein skimmer, and the addition of an ozonizer will further increase the efficiency of your protein skimmer and kill bacteria and free-swimming parasites, thereby helping to prevent disease while promoting faster wound healing, as discussed below:
Ozone (O3) is the highly unstable triatomic form of oxygen. The instability of the ozone molecule makes it highly reactive, and it oxidizes or "burns up" organic compounds and microbes on contact. As a result, ozone is widely used for water purification and sterilization, particularly in Europe (Fenner, 2003a). When used in conjunction with a protein skimmer and properly administered, it provides many benefits to the aquarium and is a very useful option seahorse keepers should strongly consider employing.
Ozone chemically degrades large organic molecules, thereby helping to raise pH, increase dissolved oxygen levels and Redox potential, and improve water quality in general while greatly increasing the efficiency of your protein skimmer (Fenner, 2003a). Its ability to destroy microbes on contact also makes it a very useful disease control measure. Virtually all the large public aquaria employ ozone in their systems for these reasons.
For best results, an ozonizer or ozone generator is used to introduce ozone into the bubble column of a protein skimmer. The outflow from the skimmer should then be discharged into a filter or sump for degassing and chemical filtration before being returned to the main aquarium (Fenner, 2003a). In the best systems, ozone is used in conjunction with an ORP controller in order to optimize and stabilize Redox (reduction-oxidation potential).
That’s what I would suggest in your case, piper. Consider installing an ORP controller to automatically control the introduction of the ozone to your aquarium. That will eliminate any guesswork as to the proper flow rate for the ozone and assure that you are not overdoing it. When properly controlled and administered, ozone can be very beneficial for aquarium, but too much of a good thing can always be problematic…
I am glad to see that you removed the Pot Belly seahorses (Hippocampus abdominalis) from your reef tank, piper. You are maintaining a water temperature of ~74°F (23.5°C) in the aquarium, and that is too warm for H. abdominalis. Pot bellies are temperate seahorses that will do best at a water temperature of 66°-68°F (19°-20° C). Sooner or later, your potbelly seahorses would have experienced heat stress in your reef tank and their health would have suffered as a result.
Best of luck resolving the issue with gas supersaturation and GBD in this particular aquarium, piper.