I am an ornithologist by training, and an aviculturist by experience, but before I started keeping and breeding birds, I kept fish, and I still keep fish now. In fact, the first pet I ever kept and bred were fish, and they were wonderful teachers for developing both a sharp eye for detail and a disciplined husbandry technique that was extremely useful later when I started keeping and breeding rare parrots. Like most aquarists, after keeping a variety of freshwater tropical fishes for five or six years, I began looking around for a group of fishes to focus my energies upon. Because I worried about the environmental ethics of keeping wild-caught coral reef fishes, I instead chose to specialize in two distinct groups, one of which were the brackish water rainbowfishes from the South Pacific Islands (where, not surprisingly, my research birds also originate).
The rainbowfishes are a challenging and beautiful group of fish to work with, but perhaps one of my favorite rainbowfish species is the Celebes Rainbowfish, also known as the Celebes Sailfish,Telmatherina ladigesi. This medium-sized, large-eyed species is a lively but peaceful schooling fish that possesses a subtle, elegant beauty. They have a slender, laterally compressed and streamlined body, adorned with two dorsal fins; the first being very small and often overlooked. The first dorsal fin is a rich amber color while the other, larger, fins are a delicate lemon yellow. The first rays of the larger dorsal and anal fins are black, and the edges of the caudal fin are yellow with bright white tips. I am always intrigued by the delicately colored tail and back half of the body since you can easily see through this region of the fish's body when the light is strong.
The belly is a dark silvery-yellow covered with shiny scales that impart a brilliant silver flash when the light is just right -- which no doubt acts as a visual signal for these fish's companions. The entire body, and especially the gill covers, have an iridescent overlay that ranges between green and blue and the lateral line is likewise adorned with a rich iridescent stripe that ranges from a dark green to blue in color. Gender can be visually identified, and adult males are especially gorgeous with their elongated, filamentous fins and characteristically deep blue-green iridescent body that shimmers over their base body color, especially during courtship.
Celebes Rainbowfish reach lengths of up to three inches (7.5 cm) as adults. They are slow-growing fish, and take at least seven or eight months to attain full size. If breeding these fish, you should set up a separate breeding aquarium filled with many salt-tolerant fine-leafed plants such as Cabomba, Milfoil, Riccia and Java Moss. The parents will scatter roughly 50-70 relatively large eggs throughout the plant leaves -- and will then begin eating them if not removed quickly. The eggs hatch within seven days and the surprisingly tiny fry eat from the water's surface. They usually are large enough to add to the main school by the time they are five months old.
While fry and young fish live near the water surface, the adults typically spend most of their time zipping around with their friends in the middle two-thirds of the water column, so I kept them with other brackish fishes that utilized either the top or bottom regions of the aquarium; Celebes halfbeaks, Nomorhamphus celebensis, which only tolerate brackish water, and another truly brackish water species, bumblebee gobies, Brachygobius xanthozona -- both of which are fascinating species in their own right. (NOTE: Halfbeaks breeding and also be aware that there are two similarly marked bumblebee gobies --make sure you are getting the brackish water specialist).
Celebes Rainbowfishes are omnivorous in the wild, but they eagerly accept a large variety of foods in captivity, especially live and floating prepared foods. I varied their diet daily between floating flaked foods, live or flash-frozen Tubifex worms, bloodworms, and brine shrimps. Brine shrimps were particular favorites, so I ended up feeding this as the main part of the rainbowfishes' diet. I never fed insect larvae to my rainbowfish, but they also accept these eagerly -- but be sure that the source is pesticide-free.
I kept my rainbow fishes in a 55-gallon aquarium, which is larger than the "minimum recommended size" for this species. Because these fish always used that "extra" space and appeared to be so much more comfortable in large areas, I argue that it is best to always keep active fishes such as rainbowfish in the largest space possible. Certainly, if I had not moved to NYC, my plan was to increase their numbers and to provide them with a 100 gallon aquarium.
This species is very sensitive to water conditions, so they can be extremely challenging to keep in certain regions of the country. However, I was lucky because I lived in Seattle, Washington, where the water was naturally clean and soft, and its chemistry was easily altered. Perhaps the most crucial help for maintaining and buffering water pH and hardness was my choice of coarse crushed coral as the aquarium sand. Despite frequent water changes, this medium maintained water hardness between 10-20 dGH and pH between 7.6-7.8. I changed the water twice or thrice per week (this is the bare minimum, in my experience); removing between one-tenth and one-fifth of the water volume midweek and replacing with fresh water, and replacing one-half of the total water volume on the weekends, and adding either rock salt or sea salt (7.5 teaspoons salt per 10 gallons (10 g/10 L) of added water) to re-establish salinity levels. Overall water salinity hovered around 1%, but dipped to 0.8-0.9% after midweek.
Recommended water temperatures for this species range between 70-80 degrees, so I opted to keep my fish at 74 degrees (23 C) because the other residents of the aquarium (bumblebee gobies and Celebes halfbeaks) preferred slightly warmer water temperatures (it is interesting to note that fish kept at the cooler temperatures within their recommended range tend to live longer, all other things being equal). Additionally, Celebes Rainbowfish tend to spawn more readily at cooler temperatures, preferring temperatures between 70-73 degrees (21-23 C). During the summer months, when ambient temperatures soared, I would drop ice cubes into the aquarium to prevent water temperatures from exceeding 80 degrees, to prevent the fish from becoming distressed. Even though the rainbowfish (and halfbeaks) actively investigated these ice cubes, they never experienced any ill effects from the temperature differential and the overall cooling effect was to their benefit.
Because the Celebes Rainbowfishes originated in the slow-moving estuarine waters in the foothills of the South Pacific island of Sulawesi (Celebes), Indonesia, I tried to mimic those conditions by creating a moderately fast current in my aquarium. To do this, I used a variety of commercially available electric pumps and filters as well as a water jet attached to an undergravel filter bed that I had constructed specifically for this aquarium. The resulting water current was considerably slowed by traveling through the leaves of many large live plants that I cultivated (Hornwort, Water Wisteria and Java Moss).
Even though it is recommended that these fish are kept in groups numbering at least five individuals, my experience has been that six is the minimum number for this and every other schooling species. I typically kept groups of 24-36 rainbowfish -- always in even numbers so everyone had a special friend. I also found that keeping larger groups provided the fish with the opportunity to engage in natural behaviors that they might otherwise not often display, and further, they also appeared to be more comfortable in larger groups. However, due to their expense and limited availability, it can be difficult to find Celebes rainbowfish at all. So when first establishing this species in your aquarium, I recommend that you wait to do so until you manage to find at least six healthy individuals to start with, and later, more individuals, pairs or trios can be added to that initial group.
When adding new rainbowfish to your aquarium, I strongly recommend that you exercise caution because this species is quite sensitive to water conditions: allow the water temperatures to equalize across the walls of the container. Only after temperature equalization has occurred (after 20 minutes or so) should you begin mixing aquarium water into the water that the new fish arrived in. To do this, add small volumes of aquarium water to the new arrivals' container every fifteen minutes or so. After the aquarium water volume has exceeded the total volume of the new arrival's water, gently remove the new arrivals from their container and release them into the aquarium (do not pour their water into their new home because this can introduce parasites or diseases into your resident fish population).
There are many rewarding aspects about keeping these lovely fish, but I found one special attribute of the Celebes Rainbowfish that you are probably not aware of: they love sunlight. So my secret tip for successfully keeping this species is to place their aquarium so that it is exposed to morning sunlight. I spent many early mornings sitting in front of their aquarium in my pajamas, drinking coffee, enthralled by their intense courtship displays where both sexes were transformed from their delicate silvers and yellows into deep vivid greens, blues, and purples, and zooming through their home, demonstrating what seemed to be a general joie de vivre that was highlighted by a glowing sunrise.