Spotted Garden Eel Questions

[Northwest_Scapes_]

Heyo! So in the near future, I'm upgrading my Macro Algae Tank from a 20 Gallon to a Standard 55 Gallon and thought this might be the perfect setup to make a super deep (sandbed) side for 2-3 spotted garden eels! Of course I've done some research but I was wondering if any Garden Eel Keepers can help out with some questions I have?

-Would the CaribSea Fiji Pink or Special Grade sized sand do well for them? I've heard you want sand that's not too fine since their burrow can collapse, and not sand that's too big or else they can't burrow at all. If not, what Grain Sized Sand would work well?

-Ive heard they like low flow, would having them near the spray bar (the lowest flow part in the tank) be a good idea?

-Would it be best to just have there area bare of anything but sand, or would adding things like Seagrass / Eel Grass / Caulerpa of some species work in their favor?

-Any fish suggestions on what would work well with the eels? I was thinking of things like Blue Stripe Pipes, Trimma Gobies, less aggressive damsels, a pygmy angel of some sort, etc.

Any other tips are welcome! Of course if i do go with this plan, I'd plan around the eels to try and accommodate their needs. This is just an idea, but the upgrade won't happen for a couple months

 

[Jay Hemdal]

Heyo! So in the near future, I'm upgrading my Macro Algae Tank from a 20 Gallon to a Standard 55 Gallon and thought this might be the perfect setup to make a super deep (sandbed) side for 2-3 spotted garden eels! Of course I've done some research but I was wondering if any Garden Eel Keepers can help out with some questions I have?

-Would the CaribSea Fiji Pink or Special Grade sized sand do well for them? I've heard you want sand that's not too fine since their burrow can collapse, and not sand that's too big or else they can't burrow at all. If not, what Grain Sized Sand would work well?

-Ive heard they like low flow, would having them near the spray bar (the lowest flow part in the tank) be a good idea?

-Would it be best to just have there area bare of anything but sand, or would adding things like Seagrass / Eel Grass / Caulerpa of some species work in their favor?

-Any fish suggestions on what would work well with the eels? I was thinking of things like Blue Stripe Pipes, Trimma Gobies, less aggressive damsels, a pygmy angel of some sort, etc.

Any other tips are welcome! Of course if i do go with this plan, I'd plan around the eels to try and accommodate their needs. This is just an idea, but the upgrade won't happen for a couple months

FWIW, here is an article I wrote on garden eels (over 20 years ago perhaps?) Hass's is the species you are considering...


Garden Eels

Diving off New Providence Island in the Bahamas some 20 years ago, I swam above a sandy plain near a coral reef, towards what looked to me like a scattered field of seagrass. As I approached the area, the grass seemed to be getting shorter and the growth sparser. Moving a little closer, I stopped and blinked; what had been a field of seagrass was now just barren plain of sand. The fact that I’m a bit near-sighted probably contributed to what was obviously an illusion; the “seagrass” was in reality a colony of garden eels, the first one I had ever seen. Based on their unique habits, I knew they would be extremely difficult to collect, much less to ever display in captivity. Moving forward 10 years, the next garden eels I saw were while touring a neighboring public aquarium. They had a small colony of Hass’s garden eels, (Taenioconger hassi) on display in a large seagrass / lagoon exhibit. Their visitors seemed totally enthralled by the tiny eels. I had seen this species offered for sale by importers from time to time, but had always avoided them, thinking they would be impossible to maintain in an aquarium. Well, after seeing their exhibit, the gauntlet had been tossed down, and I was now determined to exhibit garden eels for our visitors as well.
The first step was to identify and solve any unanswered questions that might impede our development of a garden eel exhibit. Although public aquariums freely exchange information between institutions, there simply was not that much information about these creatures for us to share, so there were many unanswered questions. These questions are very similar to those that an advanced aquarist must ask themselves whenever they contemplate acquiring a species they are unfamiliar with:

1) Which species would do best in captivity? I had seen Hass’s garden eels infrequently offered for sale, but never any of the other four or five common species which are found in regions where most commercial tropical fish collectors operate (The Caribbean, Indian Ocean, Red Sea and the Sea of Cortez). Over a period of three months, with a lot of searching, we managed to acquire 10 Hass’s garden eels, five gold-banded garden eels, (Gorgasia preclara) and three Caribbean garden eels (Heteroconger halis). Many of the gold-banded and Hass’s eels were never seen to feed, and the ones that did not feed died after five to eight weeks. The Caribbean garden eels would feed, but they were very nervous fish, and had a tendency to vibrate their tails so rapidly while attempting to adjust their burrows, that the tails became abraded and infected - a subsequently fatal complication. Only one of the gold-banded eels eventually began feeding, but it was found dead in its burrow two days later. Four of the Hass’s garden eels were seen to feed fairly well. It seems then, that the Hass’s garden eel is best suited for display, but at that, they are very difficult to get to feed, and losses of greater than 50% can be expected during the first two months.

2) Could we locate a supply of healthy eels of the proper species? Because of the extreme difficulty in capturing these fish, drugs are apparently always used to extricate then from the substrate. In the case of collectors in the Caribbean, the drug of choice would be the relatively benign quinaldine. What drugs would collectors use in the Indo-Pacific region? Obviously, the use of sodium cyanide would be highly suspect. Would this chemical cause residual damage in the eels as it has been accused of causing in other fish? Collectors cannot simply dig the eels out of the sand, they can burrow faster than a person can excavate. While moving two Hass’s garden eels from their quarantine tank to the exhibit, we used tricaine methanesulfonate (MS-222) as an anesthetic. A 1000 mg/l stock solution of MS-222 was squirted down each of the eel’s holes. It was expected that the eels would emerge from their burrows when they sensed the anesthetic, but after 3 minutes, this had not happened, so each eel was carefully dug out of the sand. Due to the high concentration of MS-222, the eels had received an overdose, and neither was breathing. It took thirty minutes of manually pumping water over their gills to get them to start breathing again. Had their exposure to the MS-222 been any greater, they likely would have died. What effect would a similar dose of cyanide have on these fish? It is suspected that the failure with so many of the gold banded and Hass’s eels were due to the manner in which they were collected.

3) Could the exhibit be constructed in only a 40-gallon aquarium? Other public aquariums exhibiting garden eels have done so in large displays, ranging up to 1500 gallons in capacity. As interesting as these fish are, we could not justify devoting one of our standard 700-gallon marine displays to this single species. We did however, have an empty 40-gallon “tall” exhibit. Experience while holding eels in our quarantine system showed us that as long as the substrate was deep enough, and of the proper grain size, the eels didn’t really need too much room. Up to eight eels seemed very comfortable in an 80-gallon quarantine tank. A 10” deep layer of crushed coral mixed with fine coral sand over an under gravel filter plate worked well as a substrate for small eels. We learned that crushed coral gravel alone was too large of a grain size for most of the eels to make burrows in. Fine sand by itself seemed to pack down too tight, also not allowing the eels to burrow properly.

4) How could we keep the eels from being frightened by our visitors? These fish are extremely shy, retreating into their burrows at the slightest hint of danger. To view them while they were being held in our quarantine system required a high degree of stealth on the part of the aquarist. By sneaking up very, very slowly, you might get close enough to get a glimpse of one of the eels before the whole group suddenly pulled back into the substrate. Obviously, our visitors were not going to be that patient. We installed a panel of “one-way” glass in front of the exhibit. This material only works if the area on the viewing side of the glass is much darker than the light level inside the exhibit. We installed the special glass on tracks so it could be easily removed to wash off any water stains. Kept behind this glass, the eels ignored any activity outside the exhibit, including moderately strong pounding on the glass by some younger visitors. They did seem to react to flash photographs, which proved to be a waste of film in that when the flash went off, the light/dark ratio changed, and the front of the exhibit became a mirror, reflecting the flash back into the camera lens, ruining every shot.

5) Could we supply the proper food? Prior to building this exhibit, all we really knew was that garden eels feed on zooplankton drifting by in the current. We did however, have good cultures of live brine shrimp and mysid shrimps, and we could supply the eels either of these foods at any size. We experimented with different sizes of mysid and brine shrimp, but found that many of the eels simply took no notice of the food at all. One of our aquarists discovered that many of the specimens (of all three species) would accept newly hatched brine shrimp even though common sense indicated that it was much too small a food for fish of that size. Still, it was obvious that some of the eels would accept the baby brine shrimp at the exclusion of all other foods, so this was fed to them after first being fortified with Super Selco.

6) Would the eels have any unusual medical requirements? During the quarantine period for the eels we acquired, we had the opportunity to judge their reactions when medicating them both preventively as well as to treat specific problems. Unlike some other species of eels, all three species seemed to marginally tolerate a copper treatment for 14 days at 0.20 parts per million. No eels perished during the actual copper treatment, although the feeding rate of all of the eels that were feeding was reduced. At another time, a group of eels was given a static bath of Praziquantel at 1.75 ppm with no visible side effects. One of the Hass’s garden eels which refused to feed, (but otherwise looked very good) was tube fed every other day for two weeks. Although it never began feeding on its own, the eel was sturdy enough to survive the rather stressful procedure of capturing it, anesthetizing it with MS-222, and tube-feeding it a mixture of antibiotics and liquefied food.

7) Would the public find the exhibit interesting? Public aquarists should design and build their exhibits with the education and/or entertainment of their visitors foremost in mind. Occasionally, an animal is exhibited for more selfish reasons, simply because the aquarium staff finds them interesting. Luckily, garden eels seem to be foreign enough to our visitor’s experience for them to find them very intriguing. That combined with the ability for people to get within a few inches of the eels (due to the one-way mirrored glass) has made this exhibit a good success.

Can garden eels be kept by home aquarists? The answer to this is a qualified “Yes”. If the home aquarist is willing to establish a dedicated tank for the eels, and is prepared to supply them with live foods, (at least initially) then an intermediate or advanced aquarist stands a fair chance of success. On the other hand, mortality rates for garden eels casually placed into standard fish-only or mini-reef systems would be virtually 100%. As with other marine animals having unique husbandry requirements, (flashlight fish, cold-water species, jellyfish etc.) Many home aquarists are certainly capable of maintaining garden eels if these requirements are first identified, and then fully met.

These elongate, burrowing eels occasionally find their way into pet stores, although this means that they are sometimes purchased by aquarists ill equipped to care for them. Placing one of these eels in a typical reef aquarium usually means its demise within a few days or weeks. Public aquariums are normally better able to care for these species. One problem is that these fish are extremely shy, retreating into their burrows at the slightest hint of danger. This means that they must typically be kept in very large aquariums (so people viewing them will not be seen as a threat to the eels). To work around this problems, some aquarists have installed a panel of “one-way” glass in front of a smaller aquarium and kept garden eels that way. However, this only works if the area on the viewing side of the glass is much darker than the light level inside the aquarium.
Because of the extreme difficulty in capturing these fish, drugs are apparently used to extricate then from the substrate. In the case of collectors in the Caribbean, the drug of choice is the relatively benign, quinaldine. Drugs used by collectors in the Indo-Pacific region may include sodium cyanide. This chemical can cause residual damage in the eels, and may account for the relatively high mortality rate seen in newly collected garden eels.
Garden eels in the wild feed on zooplankton drifting by in the current. With time, some garden eels will adapt to substitute diets in captivity. At first, even live mysids or adult brine shrimp may be ignored by the eels. Some aquarists have discovered that many newly acquired eels prefer to feed on live baby brine shrimp. This seems counterintuitive given the small size of the shrimp, but even large eels seem able to locate and eat brine shrimp nauplii. Of course, it takes a huge amount of nauplii to satisfy the needs of even a small eel, and due to nutritional deficiencies, the nauplii need to be supplemented with essential fatty acids such as Selco
As will all eels, garden eels have a propensity for jumping out of tanks, especially when they are first becoming acclimated to captivity. Tightly cover the aquarium, or build high sides around the top frame using plastic panels.


Hass’s garden eel
Heteroconger hassi
Maximum size: 40cm
Habitat: Sandy slopes below 15 meters
Range: Indo-Pacific region and the Red Sea
The most commonly seen garden eel, and probably the hardiest, public aquariums may still experience mortality rates of over 75% during the first year. The condition of the animal upon its arrival is vitally important. If the eel has been languishing in a dealer’s aquariums for many weeks, (possibly being held in a small container so that it cannot burrow) it may be suffering from fatal malnutrition. One group of Hass’s garden eels imported from a dealer in Japan (where they had been kept in a deep sand tank prior to sale) did much better, with a mortality rate of around 30%.


Gold-banded garden eel
Gorgasia preclara
Maximum size: 30cm
Habitat: Sandy slopes below 30 meters
Range: Indo-Pacific
A small attractive species, many aquarists have reported poor success maintaining them in captivity for more than a month or two. Many of these eels simply refuse all food, and some arrive so weak that they are unable to form a proper burrow. One gold-banded eel finally began accepting brine shrimp nauplii, and then unexpectedly died two days later. One garden eel that refused to feed, (but otherwise looked very good) was tube fed every other day for two weeks. Although it never began feeding on its own, the eel was sturdy enough to survive the rather stressful procedure of capturing it, anesthetizing it with MS-222, and tube-feeding it a mixture of antibiotics and liquefied food.

Caribbean garden eel
Heteroconger longissimus (sometimes called H. halis)
Maximum size: 50 cm
Habitat: Sandy plains below 5 meters
Range: Tropical Western Atlantic
Caribbean garden eels will usually feed in captivity, but they are very nervous fish, and have a tendency to vibrate their tails so rapidly while attempting to adjust their burrows, that the tails became abraded and infected - a subsequently fatal complication. All garden eels require a suitable substrate. A 10” deep layer of crushed coral mixed with fine coral sand over an under gravel filter plate worked well as a substrate for smaller eels. Crushed coral gravel alone was too large of a grain size for the eels to make burrows in. Fine sand by itself seemed to pack down too tight, also not allowing the eels to burrow properly.
Heteroconger luteolus is a smaller yellow eel also found in the Atlantic and is sometimes collected alongside H. longissimus. It may be that H. luteolus is simply the juvenile form of the larger H. longissimus.