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The Pearl Danio

Posted by TFH Magazine in Tropical Fish Hobbyist Blog on May 11, 2012 at 11:34 am

The pearl danio. Photograph by Tony Terceira.

By Jennifer Wilkinson

Pearl danios (Danio albolineatus) are pretty little fish that are found in the streams and rivers of Southeast Asia: Burma, Thailand, Sumatra, and the Malayan peninsula. Although most of the ones that we see today are bred in captivity in large fish farms or, occasionally, from hobbyists who spawned the fish.
In the right lighting, these are very beautiful fish; they shimmer and glow with a bluish tinge. I noticed that in some pet shops, they just look like a plain gray fish. When mature, the females are quite a bit larger than the males, however the males are the more colorful of the two. They can reach a size of 2½ inches in length.

Keeping Pearl Danios

I purchased five half-grown fish from a pet store and placed them into a 33-gallon community aquarium. First of all, they should have been placed into a quarantine aquarium before being added to my community, however I was very lucky that these fish were very healthy and did not come down with anything. The aquarium contained several pieces of driftwood and some live plants. It also housed two Ancistrus catfish, twelve Corydoras of two different varieties, and two other kinds of danios. The parameters of this aquarium were a temperature of 78°F, pH 7.2, and the water was fairly soft. Water changes of 30 to 50 percent were done twice a week, or anytime that I over fed.
To condition these fish for spawning, they were fed frozen bloodworms, frozen and live adult brine shrimp, and several different varieties of flakes. These pearl danios were always the first in there to grab the food before any of the others had a chance. One has to make sure that enough food is offered so that everyone gets fed.
These fish do not really school, but they do spend most of their time in the top quarter of the aquarium. They would occasionally be found in other areas of the aquarium, but that was usually when they were chasing food. Unlike other danio species that I have kept, the pearl danio is a very hyper fish; it doesn’t ever seem to slow down.

Breeding

Pearl danios usually breed over fine-leaved plants, however with my fish, it didn’t seem to matter if plants were available or not. In one of my spawns Java moss was available, however for other spawns it was not. It is quite difficult to tell when these fish are actually breeding because they are so hyper all the time. When they are breeding, they dart around quickly, the male beside the female, and they will slow down—not really stop over the plants or whatever else they are breeding over—and release the eggs. The eggs fall to the bottom and will be eaten if they are not hidden or the parents removed right away.
When breeding action was noticed in the 33-gallon community aquarium, the five fish were moved to a prepared 10-gallon breeding aquarium. This aquarium had a 5-gallon black undergravel filter plate that was held down with aquarium-safe rocks. The rocks had to be placed over the holes where the up lift tubes normally are so these breeding fish could not get underneath and eat all the eggs after the spawning took place. A large clump of Java moss was also placed in beside the filter plate. The water level was down to about half of the aquarium’s volume. The temperature was 78°, pH 7.2, and the water was soft. No filtration was used, only an air stone on very low.
The five adult pearl danios were left in the 10-gallon for two days, then they were moved back to the 33-gallon community aquarium. When the filter plate was removed, the bottom of this aquarium was covered in tiny, clear eggs. These eggs are not sticky, so if some were on the filter plate they would just fall to the bottom. It took three days for all to hatch and another three days for them to become free swimming.

Feeding the Fry

As soon as the fry are free swimming they must be fed. The first food for these very tiny fry was artificial plankton rotifers, and it was fed in small quantities. Some hobbyists just sprinkle it on the top of the water, however I take a very small amount and mix it with water from the aquarium, then pour it in gently so as not to disturb the fry very much. I also do a water change every three days before I add it again. The water changes must be done with a small hand siphon in a very gentle manner so as not to pull out all of the fry. If the fry are accidentally pulled out, they can be put back in with a plastic eye dropper. It is impossible to use a net because these fry are really tiny.
With each water change, a little extra water was added so that the aquarium was full when the fry were big enough to take the flow of a filter. At about three weeks of age they were introduced to baby brine shrimp. At this point most could eat it, and those that couldn’t didn’t survive long. With baby brine shrimp being fed daily, water changes had to be done every night. Baby brine shrimp pollutes the aquarium water very quickly. Shortly after, an outside power filter of the appropriate size to fit the aquarium was added. It was set on the lowest setting, and a sponge was added to the intake tube so none of the tiny fry would get pulled in.
There were so many fry in this spawn that they were moved into a bare 66-gallon aquarium to finish growing out. Most pet stores are happy to take this fish off your hands, however I did run into a few that said they could not sell these fish because they had no color, and therefore they didn’t want them.

Experiments

Since the first spawn, I have tried some different things when raising these fish. On one occasion I thought it would be interesting to breed and raise two kinds of danios in the same aquarium at the same time, but no, this does not mean cross breeding.
The breeding aquarium was set up the same way as the one mentioned above. Then D. albolineatus were added. They were left for two days, then put back into their community aquarium. I then added two pairs of leopard danios to the breeding aquarium. They were removed the next morning.
When I removed the filter plate the bottom was covered with tiny little eggs—they were literally everywhere. It took all the eggs between one and three days to hatch. This was a good indication that I had eggs from both kinds of danios. It took another four days before all were free swimming. After about a week there was a definite difference: one showed a line along the length of the body and the other fish were a beige color. At this point I wasn’t sure which ones were which. The beige color ones turned out to be the leopard danios, while the ones with the glowing line turned out the be the pearl danios. The leopard danios seemed to grow slightly faster than the pearls. Perhaps that is because the pearl danios are much more hyper, but I’m not sure.
This was quite an enjoyable experiment and quite educational as well.
On another occasion, my cories were breeding up a storm, and there were no aquariums left to raise these eggs, so I moved some of them into the 10-gallon that already contained week-old pearl danio fry. To my surprise, this actually worked! I thought that the cory eggs would fungus because the rotifers were being fed. Instead I ended up with several cory fry. Of course, with so many fry in this 10-gallon aquarium, they had to be moved to larger quarters sooner than normal. It was a good thing that some of the other fish that I was raising were ready to find new homes.
It is not a good thing to over stock the fry aquariums, after all, we are striving for strong, healthy fish. We definitely do not want to see stunted fish. In this case, I knew that the other fish would be finding new homes soon, or I would not have tried raising the cories and so many danios at all.

Try Pearl Danios

The pearl danios are a very pretty community fish that do not seem to bother any of other inhabitants. I have housed them in several different communities now and have never had a problem with any of them. The lighting has to be right or they may just look like a dull, gray fish. Remember that they will spend most of their time in the top quarter of the aquarium. The fry that were raised started breeding when they were seven months old. I kept my original five pearl danios for over two years before I gave them away. I did keep some of the fry though.

Posted in TFH Extras by TFH Magazine on May 11th, 2012 at 11:34 am.

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