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Celestial Pearl Danio

Fish new to the hobby, such as the celestial pearl danio, need more help than older, proven species.

By Joshua Wiegert and Robert Rice

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celestial pearl danio

The craze for celestial pearl danios continues, which means that the future of these fish in the wild is still not secure. Photo by Tony Terceira

For freshwater hobbyists, it can be difficult to find something new and exciting. While it is hard to imagine that there’s an aquarist anywhere who has seen even half of the available freshwater fish, we can easily become jaded into thinking of certain fish as just another dwarf cichlid, or just another killie or just another type of platy. This is particularly true as our independent fish stores are gradually gobbled up by large chain stores, leaving little room for the unique, the new and the exciting.

That’s probably why the celestial pearl danio, previously known as the galaxy rasbora, made such a big splash a year ago. For those not familiar with it, the celestial pearl danio is a recently discovered fish. These beautiful fish are named for the attractive, starlike pattern across their back as well as the drink you’ll need when you see the price tag.

A New Beauty
This isn’t a big fish. Huge individuals might crack the half-inch mark, but only if they stretch.

Even small aquarium fish, such as neon tetras or glowlight tetras, outgrow this fish and become more than double its size. The beauty of celestial pearl danios charmed many aquarists into purchasing a school of them, with many hobbyists setting up species aquariums to do so.

When first introduced, a school of five or six of these guys could easily set aquarists back a $100 dollars or more. In a few months, however, they had come down in price, with retail prices now around $6 or $7 dollars, which is still a lot for a tiny, schooling fish.

The celestial pearl danio fish was discovered in Burma (Myanmar) in the summer of 2006. It was announced to the world through the British magazine Practical Fishkeeping and quickly made its way to distributors. Not long after, it made its way to the United States. Even with its initial high price point, aquarists wanted this fish, and they weren’t disappointed. Collectors quickly moved in to satisfy the demand, and celestial pearl danios swam onto the market.

New Fish; Same Problems
Now, as those of us who like smaller fish can attest, something they lack over their larger brethren is hardiness. Smaller fish are more delicate. Wild fish are more delicate. Fish that we know almost nothing about are extremely delicate. Lots of celestial danios died. They often couldn’t handle the stress of shipping and huge numbers died in transit.

They also couldn’t handle our water chemistries — they need very soft, very acid water — and many more died. They couldn’t handle the stress of being in aquaria: they’re shy, don’t like movement and need lots of cover. Many never ate, and feeding them was made more difficult by their small size (brine shrimp and black worms are too big). And even more died. The majority of these fish removed from the wild died. Many succumbed before even reaching the retail level, let alone the hobbyist level.

Trouble Back Home
To keep up with the demand, collectors destroyed their habitat. A Practical Fishkeeping article (May 2007) reported that “just six months since its discovery … [galaxy rasboras] are facing the threat of being wiped out by the aquarium hobby.” Their natural habitat is mostly flooded wetland, with emergent vegetation making up the bulk of the habitat. Much of this has been trampled and destroyed by fish collectors.

Fortunately, the celestial pearl danio has two things going for it. Much of its habitat remains unknown and may be inaccessible to collectors. Also, it is a danio, and danios are not hard to breed. The celestial pearl danio is no exception — once one masters keeping it alive. Reports of captive breeding are coming in with some frequency, and captive-bred rasboras should hit the market soon.

Past Experiences
This is a familiar pattern among freshwater fish. Take the gorgeous black and white striped zebra pleco. When it was discovered aquarists charged to the market, bringing back tons of fish, even though no one knew how to keep them alive. Most of those first zebras died.

Many aquarists had no idea that pleco fish could be aggressively territorial. Wholesalers and retailers put more than one per aquarium, and many aquarists, who hoped to breed them, followed suit. When they woke up the next morning and found one dead, it was mysterious. Everyone knows that plecos eat algae. So, when a zebra pleco died in an aquarium full of algae wafers, it was because they’re hard to keep and wouldn’t eat, not because they’re actually carnivores, right?

Just the same, demand remained high, partly to replace the number of fish which were killed. Eventually, numbers in the wild suffered. While some governments have trouble recognizing environmental problems and reacting decisively, the Brazilian government had no such qualms. They moved quickly to severely restrict the collection and exportation of the zebra pleco.

By that time aquarists had figured out how to keep zebras alive, and some were even being bred. But the supply was minimal. The zebra pleco had come down in price to about a $100 dollars or a little less. But their price has skyrocketed once again. The silver lining: these fish are bred and raised in captivity.

Rarity and Price
The nomenclatural history of the redlined barb is a little confusing. Wholesalers and retailers were placing it in the same genus as the similar true Siamese algae eater (Crossocheilus siamensis), even though it was actually Puntius denisonii. Common names are similarly confusing, with it being variously called redlined torpedo barb, redlined barb, redlined algae eater, rose shark, Denison’s barb and others. We’ll stick with redlined barb.

Under any name, it is a beautiful fish. In the late 1990s and early 2000s, as the planted aquarium craze really began to take off, unusual and beautiful algae-eating fish saw a boom in popularity. Ameca splendens were being sold in retail stores for perhaps the first time. The gorgeous redlined torpedo barb took the planted aquarium crowd by storm. Here was a brightly colored, peaceful fish that gobbled up algae with the same gusto as a Siamese algae eater. The downside was its larger size (about 6 inches or so) and its higher price.

A Vicious Circle
Early on there were few redlined barbs being circulated by only a few collectors. As a result, the few that made it to price lists commanded a high price. As the demand rose and more collectors entered the market, the price dropped until the redlined barb was selling for more affordable prices — about $20 each. But many aquarists were unprepared for their larger size. These big, active, shoaling fish need an aquarium of 75 gallons.

Redlined barb fish proved robust in aquaria, surprising for a fish new to the hobby. The major difficulty with them ended up being their need for highly oxygenated clean water, but this was not too difficult to achieve in most planted aquariums.

Unfortunately, they have proven almost impossible to spawn in captivity. (Some captive breeding occurs with the aid of hormone treatments, but this is beyond the scope of most aquarists.) They were caught and shipped from India. The aquarium hobby and development took their toll on these fish. As a result, redlined barbs quickly became threatened.

A common theme runs through these three very different fish. Each appeared on the market and had instant success as true “wow!” fish. In response, they soon became overcollected. Fortunately, celestial pearl danios, zebra plecos and redlined barbs are still available in the hobby. Provided species can be bred and maintained by hobbyists, the hobby invariably acts as a sort of ecological safety net for many fish by preventing them from disappearing altogether.

Making a Difference
Aquarists dictated demand for these fish, which put heavy stress on their wild populations. While it is easy to blame collectors, each of these fish comes from an impoverished area of the world, as do the vast majority of our tropical fish. Fish collecting is often a means of subsistence for people in these regions, and you certainly can’t blame them for trying to put food in their bellies. Instead, the blame lies with those in the hobby who fueled the initial heavy demand for these fish.

Part of responsible fishkeeping is keeping only those fish that will survive in aquaria. When a new fish enters the market, it’s easy and natural to want to try our hand at it, particularly when we’ve been successful with other fish. If the fish is a good aquarium candidate and particularly striking, it will be in the hobby for the long haul, provided it survives us.

Often, we hear: “Hi, I bought some fish I know nothing about, and now I want to know how to not kill them.” This is followed by the inevitable reply: “Never buy fish you know nothing about. Take the time to find out the husbandry requirements of a fish before purchasing it. Here’s how to keep your fish alive ...”

As responsible aquarists, we know this is good advice and try to follow it. Not only is it best for the fish, but it is best for the aquarist too. We all know someone who purchased a school of cute, silvery bala sharks for their 10-gallon aquarium, only to find out later that they will outgrow such a setup.

But when something new and exciting comes on the market, we give into temptation and ignore our own best advice. We spend a lot of money to buy a school of these hot new fish, and nine times out of 10 we succeed in killing them. Let’s face it, there are much better things to do with a couple hundred bucks than kill some fish.

And the worst effect may be in driving up demand for these fish, which can manifest itself into heavy habitat exploitation and destruction and even lead to the removal of certain fish from the hobby (e.g., Brazilian restrictions on zebra plecos). The better alternative would be to have only dedicated aquarists initially purchase such fish and puzzle out their captive-care requirements. Once a new fish’s husbandry and breeding protocols are revealed, then the general hobbyist population gets the green light to acquire that particular fish.

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