The actual cause of Gas Bubbles is poorly understood. Sadly there isn't enough research into this on seahorses. My understanding from seahorses that have been necropsied is that it is most commonly bacterial in nature. Experience in dealing with this, is once you have these issues in a tank, it most commonly keeps rearing it's ugly head from time to time. When you have high stocking densities, you may resolve it in one only to find it appear in another. Antibiotic and Diamox therapy seems to temporarily resolve it but don't be surprised to see it again.
Water quality as mentioned seems to be the underlying cause. Specifically, organic loading of the system. High amounts of dissolved and nondissolved organics ultimately lead to issues. When we help folks with Gas Bubble Disease (GBD) or Pouch Emphysema (PE), we focus on reducing organic loading of the system. This usually resolves re-occurring PE and some cases of GBD. For GBD it really depends upon the actual bacteria involved and the immune system of the animals.
For short term treatment to reduce the bubbles, Diamox is very effective. Treatment should be in a hospital tank with Diamox at 250 mg per 10 gal. Each day do at least a 50% water change and redose at 250 mg per 10 gal. Treatment usually takes 3 to 5 days to reduce the bubbles. Diamox works by reducing the bubbles but does not treat the underlying cause. Many will do a concurrent treatment with antibiotics. Diamox can be mixed with antibiotics without issue. As stated above, sometimes you can move the animals to clean water and the bubble will resolve themselves when the seahorses immune system kicks in.
As mentioned, 16 seahorses in a 85 gal tank is a very high bio-load. My personal preference for a display tank is roughly 25 to 30 gallons per pair. This high of a load is usually only successful long term (18 mos or longer) in production systems which have a beefed up filtration and husbandry scheme.
If I were dealing with this, here is how I would approach it:
1. I would review the feeding regime. Rinsing the frozen foods well with tap water will help remove any excess nutrients. I would not try to enrich the frozen foods as most of it will come off in the water and lend to the organic loading. I would also make sure the tank is not over fed and if it was siphon out any excess.
2. I would review the filtration scheme. Flow in the tank should be at least 10 turns per hour. I would run more if I could break up the flow so the seahorses are not blown around. High flow will help keep the organics in suspension so the filtration can remove them. I would also look at the filters. This high of a load you want really good tight filtration. A 50 micron filter sock will help catch a lot of the larger particulate matter and will likely need to be changed often. I also like cartridge filters for high density systems and usually go to small micron filters. A high performance protein skimmer would be a must.
3. I would also take a look at the substrate. With a high stocking density most production tanks are bare bottom for a reason. It is easier to remove the waste on the bottom. Daily siphoning removes uneaten food and excrements. I would at least have a fine sand bed. If it was anything coarse, I would remove it and go with a fine sand bed or bare bottom.
4. I would also consider running either ozone or an Oxydator to help eat up excess organics. For this size of a tank and the stocking, 2 Oxydator A's or 1 Oxydator A with double strength peroxide would work.
5. If probiotics are not being used, I would definitely consider them. Certain strains are very good at eating up organics and compete against bad bacterial strains.
6. I would scrub all surfaces in the tank and sump that can be scrubbed to remove as much of the biofilms as possible. I would also clean the piping with a pipe brush. After doing this, I would add 2 to 3 teaspoons of regular peroxide (1 to 1.5 mg/L) to the tank. The peroxide will help eat up the organic material. Depending upon the microbial life in the system, the tank may temporarily become cloudy. This usually clears in a few days. I would probably consider adding the peroxide daily for 1 to 2 weeks. Usually the water becomes noticeably clearer.
7. I would keep the system as cool as possible or down to 69 degrees. Cooler temperatures usually slow down bacterial growth. This gives the seahorses immune system a better chance at fighting what ever is going on internally.
8. I would consider boosting the seahorses immune systems with Allicin, Vitamin C, Beta Glucan and Probiotics. This is usually best done by adding this to a good high quality enrichment and gut loading adult artemia (brine shrimp). Allicin is the component in garlic that is so good at fighting bacteria, fungus, viruses and parasitic issues. In humans it has been proven to even work on Mycobacteria. You will need a stabilized version, not just garlic extract. Any product with Allisure AC-23 will work. Vitamin C is best with Stay-C or Ascorbyl Palmitate which artemia readily convert to free Ascorbic Acid. The Probiotics I would go with a product that has been proven in aquaculture such as Inve's Sanolife.
I know this sounds like a lot, but I have used this strategy successfully many times. With high density systems like you have, they are rarely successful long term unless you aggressively attack the organic loading issue and keep the immune system of the animals up.
Lastly, there is the simple solution. Go to a light stocking density system, 4 to 6 seahorses, in which the normal filtration and husbandry works.
Dan
