I apologize it took so long, but as promised I am posting the recent discussions on a listserve and hopefully adds some value to your questions. On a side note, I am not recording whom these replys are from, but an assemblage of various professional aquariums within the U.S. and international;
"We are in the process of acquiring a group of Heteroconger hassi, and a few husbandry questions have come up; There is some concern that the animals may suffer additional risk of injury during the course of a separate quarantine stop / transfer. Would there be any significant advantage to carrying out preventative medication on exhibit? How vulnerable are they to injury, infection or parasites? Which infectious diseases or parasites in particular? Would a five day nitrofurazone treatment and thirty days on copper be suitable? We are deciding between a 50/50 mixture of silicon filter sand and slightly larger aragonite gravel, or the silicon sand on its own. Is either substrate preferable or should we be looking at something different? Do you have any other advice which would be helpfull?"
"We have currently got a population of about 25 garden eels. Upon Arrival we gave them a PRAZI treatment, Apart from this they spent next to no time in quarantine, not sure if this was a good thing but our survival rate was exellent. We got them out onto display as soon as possible. With regards to substrate we have found a fine coral sand to be sufficient roughly 4 inches deep. I personally would not try anything to coarse."
"We have a group of the same species here. When they arrived, we chose to quarantine them on exhibit to minimize stress as it would be hard to set up a suitable quarantine tank. There was nothing else in the exhibit before the eels went in, so there was not too much concern about doing it this way. The only thing that we treated with was Baytril. They are in 8-10 inches of fairly fine sand. I would definitely, also, steer away from anything too coarse as it seems to be bothersome to them and they do not seem to thrive in it. I should also point out that there is a return manifold under the sand to help keep it from getting too compacted. When doing gravel vacs on it, I only dig less than 1" into the sand, and there has not been any problems with this."
"Unfortunately once introduced into any exhibit, pathogens can easily become established, hence quarantine, which is designed to isolate specimens to prevent the risk of pathogen transfer, even into na
ďve exhibits. In future, all South African public aquaria are going to have to comply with biosecurity regulations, which prohibits the movement of fishes between areas without health certification. This will have an impact on quarantine protocols and the sterilisation of effluent water from exhibits (public aquaria-general) / fish farms etc. I know this all sounds “out-there,” but we need to begin planning quarantine regimes, even if only for isolation periods at this time. Where are your eels coming from? If internationally, what country? To answer your questions about susceptibility to infection and what pathogens, it depends on several variables. If your eels are kept relatively free from stressors, and their husbandry is good and their feeding requirements met, you should have fewer problems. They DO seem to be susceptible though to injury as you suggested, which can become secondarily infected. On parasites, I stand corrected in suggesting that little or no parasitology has been done for these species, though the ubiquitous parasites Amyloodinium ocellatum and Cryptocaryon irritans are quite possibly “usual suspects.” On Nitrofurazone use, please remember that antibiotics should be used as an active treatment according to a known infection and antibiogram, and not really as a prophylaxis. I do understand your concern about preventing infection of possible lesions caused by transfer of the animals between quarantine and exhibit, but in the long run, as seen with the drug Enrofloxacin, we will be faced with future resistance. Try to rather prevent any injury first, maybe by anaesthetising them to facilitate stress-free."
"Has anyone seen a relationship in how far garden eels, Heteroconger hassi, will come out of their burrows and water height/depth above them? Or any relationship on how far they come out and light intensity?"
"I haven’t noticed any relationship regarding water depth and how far our H. hassi come out of their burrows, mostly because the tank we moved them into was not much deeper then their old one. The eels in their old tank where very shy and did not display well during public hours, when we introduce them to their new habitat with a greatly increase flow and not much but a bit lower light levels and I have found that the eels seem a lot more comfortable and come farther out of their burrows more often."
"For those of you with Garden Eel exhibits, I am curious as to how many times/day you are feeding them."
"We feed our garden eels cyclopeeze, frozen mysis and ground gel diet twice a day. Usually once in the morning and then a second feeding shortly before we leave for the day."
"Two or three times a day with a variety of frozen foods and live artemia."
"We have a stable population of garden eels that have been on exhibit without replenishing for about 4 years. We feed small chop mussel/fish or gel once a day with bonus nauplii a few times a week in the afternoon."
"We feed our Heteroconger hassi twice daily, in the morning we feed frozen mysis, brine shrimp, and we start a drip bucket with cyclopeeze/artemia nauplii. Then in the afternoon we feed either plankton, flakes or gel diet."
"We 're planning to opent a new tank (Lg3,5Xlg1,5XH1,5) displayng
garden eels with some other fishes (basslets, cardinal and glassfish). Does any one have such experience and or advise ?"
"I don't remember exactly the name of Garden eels genus (Heteroconger or Gorgasia perhaps) that we worked with. Our tank was more or less 0,5m3. For the sand size, they use to work with coral sand not very big (2-3 mm grain size). Filtration system with airlifts and food... live enriched artemia and/or overall live mysis (2-3 times per day)."
"many aquariums exhibit H. hassi with other fish so I don't see a problem though these tend to be large exhibits. I have seen H. hassi and Gorgasia species in tanks at Sunshine Aquarium, Tokyo (1000 gallons?), Aquamarine Fukushima (20,000 gallons), Henry Doorly Zoo (500 gallons?)and the Georgia Aquarium (15,000 gallons?)."