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Wednesday, February 23, 2005
In the beginning, there were the simple primitive chordates that evolved from tunicates. Jawless ostracoderms started it all off, giving rise to Agnatha (lampreys) and Myxini (hagfishes). Agnatha gave rise to another set also called Agnatha, still without jaws, and to the gnathostomes, who had jaws. From the gnathostomes came the Osteichthyes and Chondrichthyes, the cartilaginous fishes, who brought forth the Holocephalans (chimaeras) and the Elasmobranchs (sharks and rays). The bony fishes Osteichthyes started off the Sarcopterygii (lobe-finned fishes), that spread forth the Dipnoi (lung fishes) and the Crossopterygii (the barely extant coelocanth) from whom came the Rhipidistomes, who gave rise to tetrapods and eventually us! Osteichthyes also brought forth the Actinopterygii (ray-finned fishes) who started off the Chondrostei (sturgeons) to Neopterygii, which consists of the Holostei (gars and bowfins) and finally the Teleostei, the true bony fishes, which includes bigger fish like tuna and salmon, as well as the little cichlids and characins we like to keep in a little aquarium.
Sparky's New Home
Sparky the black phantom tetra (Hyphessobrycon megalopterus) was the first resident of a particular five gallon tank in a humble suburban Maryland home. Feeding on dry flakes of fish meal, wheat flour, wheat gluten meal, menhaden oil, and various other ingredients, he lived alone for almost a month. The black phantom tetra originally comes from river basins in Paraguay and likes benthopelagic freshwater with pH between 6.0 and 7.5. They enjoy being in groups of five or more. Sparky, however, remained the only one of his kind in the tank.
Filter and BIO Wheel
Loneliness wasn't all bad for little Sparky. Being the only fish there, he was not as ecologically stressed as if there were several fish. Stress wears down immunity thus making him vulnerable to the numerous dangers of the innocent home fish tank. Ammonia is a big problem as it is very toxic, and things like dead fish, uneaten food, and other factors raise its levels. Aquarium filters often come with biological filtration, which is a wheel of special bacteria that convert ammonia and the less dangerous ammonium into nitrites and nitrates, which are still harmful in really high doses but much better than the former. This process uses up a lot of oxygen though, which is one of many reasons frequent water changes are so necessary.
Sparky lived nicely until about a month after he got here. Two new fishes joined him: a big neon tetra named Floyd and a red eye tetra named Cedric.
Epidemic
Along with the two new fish came a ghost shrimp called Crusty. He (?) minded his own business, scouring the bottom and any surfaces for stray matter to eat. Small and hard to see, but he did his job. Meanwhile, coy new fish Floyd the neon tetra (Paracheirodon simulans) kept to himself, not eating much initially but seemed okay. Stayed away from Sparky and Cedric the red eye tetra (Moenkhausia sanctaefilomenae), who stuck by each other a lot. They were about the same size.
Not a week after the new fish arrived, little neon tetra Floyd was growing white spots all over his body. At first I figured his scales had gotten a bit messed up somehow so didn't worry about it. Water quality, maybe. I needed to change it anyway. So that's why I wasn't too concerned when Sparky got the white spots, too. In fact, I did not finally realize it was a serious problem until Sparky, unable to swim due to extreme malaise, was stuck in the filter vent! Knocked him out of there, but he could not even stay buoyant anymore. I took him out and quarantined him in a cup. His gills were still moving though, but, the next morning, less than 48 hours after I noticed he had gotten the white spots, Sparky was dead. 
Filter vent
Floyd seemed fine despite the spots, even though he'd had them for several days. That afternoon, same day Sparky died, he fell into a malaise and was soon dead. I got out to the aquarium store and brought back some copper sulfate solution to take care of the problem. For those white spots are blatant signs of Ichthyophthirius multifilis, a nasty little protozoan that is commonly called "Ich", that is spread via unsanitary tank conditions usually. Some other nasty protozoa that attack aquarium fish are Costia, Chilodonella, and Cyclochaeta, any of whom cause "slimy skin disease" which is a cloudy skin condition. There are a lot of others, too!
Copper sulfate solution is harmful to aquatic plants and invertebrates. So Crusty the ghost shrimp had to get out of the tank. I put him in a glass bowl I set up for him. Now Cedric the red eye tetra, who, by the grace of God, is a very hardy species and did not contract Ich like his tank mates, was all alone in the tank with only the deadly protozoa and the copper sulfate solution to correct it.
The next morning, Crusty was not in his bowl. I never did find him!
Cedric the Red Eye Tetra
Lone Survivor
Cedric doesn't swim around a lot. He usually stays in his own corner of the tank. Also hates it when the aquarium light comes on, since it makes him dart around and hide. So I leave it off, even though I probably shouldn't.
Aquarium lighting would be especially important if I had any live plants. Since all my aquarium plants are made of plastic, I don't worry about it. However, it also serves a purpose for the fish themselves. In their tropical river habitats, the sun is up for twelve hours each day throughout the year, and that's the way they like it. The temperate seasons here don't provide such a solar schedule, so the aquarium lamp must do the job. Ideally, the lamp should be on anywhere from 10 to 14 hours to simulate natural conditions. Too long augments the growth of blue-green algae. Certain kinds of lamps may grow too hot and make the aquarium a dangerously high temperature. It's also important for the light source to be straight up, which helps the fish know which way is up, so they wouldn't be swimming around sideways!
As summer days went on, I worried about the tank temperature. Did not want poor Cedric to be too warm. Red eye tetras and other similar species enjoy temperatures between 75-85ºF, and my tank temperature was averaging around 84ºF. It was too warm to use my aquarium heater, which requires the tank temperature to be below 82ºF. Temperature is an important factor in keeping a healthy environment. Cold water can cause rocking. Hot water can cause darting about.
Another important factor, which was briefly mentioned earlier, is pH. Acidic and alkaline conditions play an important role in many chemical processes in the tank, like conversions involving ammonia and nitrite. Too alkaline conditions can reverse these processes, causing nitrites and nitrates to actually revert back to ammonia and ammonium! Fish tend to like their water a little on the acidic side, generally at a pH between 6 and 7, but that of course depends on the species. As would be expected, extreme pH either direction has physiological effects on the fish. Symptoms of water being either too acidic or too alkaline is fish rubbing against objects or darting about. Red discoloration may be the result of acid damage. Blue or white skin dulling may result from alkaline damage. The gills are also extremely sensitive to pH.
Days of Gordon
Algae can be a problem. It grows all over everything depending on how good conditions are for it. Light accelerates its growth as well as nutrient surplus. Since I have no real plants in my tank, it wouldn't be a major problem. It is unsightly, though.
Cedric was all alone for a while at this point. So I got out to the store and brought home a plecostomus (Hypostomus plecostomus) named Gordon. He was highly recommended as a good algae eater. He was big, too. I'd say five or six centimeters. It was then I realized the trouble. This new fish was so much bigger than Cedric, who spent most of his time avoiding Gordon. A little aquarium rule: make sure the fish are all roughly the same size! I had forgotten this rule, so things got tense between the two tank mates.
Gordon did not seem all that concerned with Cedric. Didn't bother him. Didn't try to eat him. Just went about his own business sucking the walls and gravel. He did a great job! The tank was so clean. Any bits of green I saw growing on some surfaces were gone. Despite residential tension, things went well.
One day, Gordon was working on the bottom gravel. He tended to stay in one spot for a while. He was in one spot for a good long time before I noticed he hadn't moved. A glance at his frayed fins and finally poking him with the net revealed he'd been dead for an unknown amount of time! Cause of death is unknown. I had Gordon for only two weeks.
Since dead fish are such a burden on the ecosystem, a prompt water change was in order, even though I think a water change was needed anyway. Even now that there was cleaner water, Cedric was again all alone.
Jasper
For another few months, Cedric was all alone. Not a good thing for a species that much prefers being in groups. Even though he and Sparky the black phantom tetra only lived together for six days, Cedric still exhibited many of Sparky's characteristics. He stayed in one spot most of the time. Ate his flake food in a dart-like motion, darting up and down from the surface.
I didn't really notice this until two weeks ago when I brought home a platy (Xiphophorus maculatus) named Jasper. Platies vary in color, and this one is dark orange with black spots. Beautiful! They belong to the order Cyprinidontoformes and are in the family Poeciliidae. They are live-bearers, so they bear live young rather than just laying eggs like many other fish. Similar fish include the swordtails and the mollies, which the platys can interbreed with. Males lack an anal fin and instead have a copulatory organ called the gonopodium. Jasper, whom I assumed was male when I gave that name, has an anal fin, and therefore is female. She doesn't seem to be pregnant, since she does not have what's called a gravid spot just above her anal fin, a telltale sign of the expecting platy. 
Jasper the Platy
Cedric adopted some of her eating habits. Although for the most part he still keeps to his little corner, he has become a bit more of an explorer like his new tank mate. Jasper searches for food that has sunk to the bottom, which Cedric does not do, but they both scour the surface at feeding time. Cedric still darts up and down but not as much. I think they get along quite well.
But That's Just Me
That's my fish menagerie so far. It is a constant little adventure although not likely to wear you very thin. Get your own! There are lots of kinds of fish to keep in an aquarium. Mine is only 5 gallons, but more experienced aquarists than I have much larger ones. Some fish need tanks at least 50 gallons in volume. There are freshwater tanks and saltwater tanks. Community tanks and one-species tanks. You also have to watch for parasites and other maladies, such as the aforementioned Ich and even the threadworm poor Jasper has! I would love to have gone into more detail about the parasites, but it's better held off for another time. Check out the links below for more info.
Sources & More Info
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