Wikipedia:Reference desk/Archives/Miscellaneous/2012 September 16

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September 16[edit]

30 Gallon Fish tank, how many fish?[edit]

Okay so I started setting up a 30-gallon fish tank 3 weeks ago and so far have the following fish

3 Guppies 1 Molly 1 Red-finned shark 1 Green spotted puffer

I want to get another guppy and possibly a loach and a figure-8 puffer but I'm not sure approximately how many fish is healthy for the tank. Does anyone know how many fish I could possibly have in my tank? — Preceding unsigned comment added by Pennypuppy475 (talkcontribs) 02:36, 16 September 2012 (UTC)

I would think it would vary by the types of fish. Have you spoken to your pet supply store? And if it does get too crowded, put a piranha in there, and the crowd will thin out.Baseball Bugs What's up, Doc? carrots→ 03:03, 16 September 2012 (UTC)
Also consider that some fish can grow quite a bit. Catfish come to mind immediately, but that red-finned shark might also grow up to 6 inches long. You need to account for their future size, not just their current size, unless you plan to get larger aquariums as they grow. StuRat (talk) 03:08, 16 September 2012 (UTC)
Maybe I'm remembering incorrectly, but don't fish tend to grow in proportion to the size of their environment? ←Baseball Bugs What's up, Doc? carrots→ 05:12, 16 September 2012 (UTC)
Definitely not. That's a myth, and a particularly cruel one for large fish first bought as juveniles. They are called "tankbusters" for that reason, and often die from overcrowding or are abandoned by their owners. Some fish, however, will remain smaller in small tanks than what they would naturally grow to. But not because they're acclimating, but because their growth is stunted (i.e. those are unhealthy fish). Unscrupulous pet shop storekeepers will often tell you anything to sell the fish, particularly large species which they would need to get rid as soon as possible as their upkeep can become expensive once they become adults.-- OBSIDIANSOUL 12:46, 16 September 2012 (UTC)
So my plan to toss a goldfish into the swimming pool and wait for him the reach whale size won't work ? :-) StuRat (talk) 03:24, 18 September 2012 (UTC)

The standard rule of thumb is one inch of fish per gallon, assuming a slender body form like a guppy, not a goldfish. Google will confirm this generously, for example: Guppies are actually best raised alone, and with live plants, since they will breed very easily, which is great fun, until the other fish, especially the shark, (or crowded guppyadults) start eating them. Even with only guppies, I wouldn't start with more than a dozen or so adults. You can get 8 males to four females since they are prettier and this will keep down reproduction. (Eventually you will have to separate sexes due to overcrowding, but not right away.) If you begin with a reasonable number of fish and only add one at a time you will find that overcrowding will solve itself with mutual predation. That can be upsetting when your favorite fish is the most delicate. μηδείς (talk) 03:23, 16 September 2012 (UTC)

To make it possible for non-Americans to contribute here, 30 US gallons is around 113 litres. HiLo48 (talk) 03:31, 16 September 2012 (UTC)
Odd how the British always surrender to the French. That works out to 0,2655 inches de poisson pour litre. μηδείς (talk) 05:37, 16 September 2012 (UTC)
British surrender???? Never! Many of us here in the UK have not surrendered to the French! 30 US gallons is almost 25 Imperial gallons and these units are still used for fish tanks. Have Australians surrendered? If the 30 gallons were English (as BB thinks below) then to enable Americans to contribute, that's about 36 US gallons (or just over 136 of those metric things). Dbfirs 07:19, 16 September 2012 (UTC)
Surrendered? To the French? Jamais!! Alors, formidable! -- ♬ Jack of Oz[your turn] 07:33, 16 September 2012 (UTC)
Currently he has 5 fish in his English-system tank. How many fish is that in metric? ←Baseball Bugs What's up, Doc? carrots→ 05:12, 16 September 2012 (UTC)
Latin for less than one and Greek for greater. Hence half a dekaichthyon. See metric prefixes. μηδείς (talk) 05:29, 16 September 2012 (UTC)
I live in one of those countries where the Illuminati have forced the adoption of the metric-kery system, and I've just come back from a local fish-market. When I asked for half a "dekaichthyon" of flake, they just looked at me like I was a crazy person. Mind you, people quite often look at me like I am a crazy person.--Shirt58 (talk) 07:09, 16 September 2012 (UTC)
Or perhaps a flake. StuRat (talk) 07:15, 16 September 2012 (UTC)
?met? This user prefers metric units and cannot figure out why Americans have such a hard time with them.

HiLo48 (talk) 08:12, 16 September 2012 (UTC)

The converse seems to be the problem. I have never met an American (other than some women over a certain age) who is not comfortable with metrics. I had an outlandish editor who insisted (saying his younger Australian relatives didn't understand traditional measures!) on putting a metric conversion in the middle of a verbatim anecdote, to the effect of: "A journey of a thousand miles (1,609 kilometers) begins with a single step." μηδείς (talk) 17:48, 16 September 2012 (UTC)
The possibility exists that he was making fun of metrics. As those of us who like the old English system sometimes do. But he overlooked something: What's the metric equivalent of "a single step"? ←Baseball Bugs What's up, Doc? carrots→ 02:08, 17 September 2012 (UTC)
Oh, no, this guy was quite serious. His main activity at wikipedia was to change traditional to metric. μηδείς (talk) 17:14, 17 September 2012 (UTC)
All countries have their weirdos. Obviously.  :) -- ♬ Jack of Oz[your turn] 21:27, 17 September 2012 (UTC)
I was wondering what an Aussie would think of this. Even if they couldn't give the exact conversion, I would expect people, simply because they were English speakers, to have a vague notion of an inch, a foot, and a mile. How would one understand English literature otherwise? In the US I learned what a fathom and a fortnight were in English (i.e., grammar and literature) class. Surely these concepts are not verboten?μηδείς (talk) 21:34, 17 September 2012 (UTC)
Indeed not. A woman will go shopping and ask the butcher to cut her a kilo of whatever meat. Then she might drop into the hardware store to buy that couple of metres of rope her hubby needs. But then she goes into labour and delivers a healthy baby, which she announces weighs however many pounds and is however many inches long. This is true even for women who were born after we converted to the metric system, which would be most women of child-bearing age now. People still talk of quarter-acre or 10-acre plots of land, rather than however many hectares. Most people have a fair idea of how much a ton weighs or how long a yard is. They know a cricket pitch is 22 yards long. (But tell them it's a chain, and that'd bamboozle most people.) They'd have heard of pints of milk and know it was the standard quantity, akin to litres these days. Anyone who uses cookbooks handed down from their mothers has to get familiar with pounds, ounces, Fahrenheit degrees and so on. So, yes, we do have a pretty clear idea of what many of the old measures meant in real terms. Not so true when it comes to pounds, shillings and pence, which was admittedly a bit of struggle for some people even when that's all we had. That has zero practical application anymore, but it's sometimes encountered in older literature (we switched to decimal currency in 1966). Racegoers might have a better idea of a furlong than most people. Fathoms, leagues, pecks, bushels, roods, els, etc - these were always in the "not sure" basket for most people. There are no plans to abandon fortnights. Or dozens. -- ♬ Jack of Oz[your turn] 23:38, 17 September 2012 (UTC)

I know it's quite tempting, but you shouldn't buy one each of every fish you like. Guppies are great for beginners, so are Mollies (but both species should be kept in groups - either all male or with more females than males, otherwise the females will be chased all the time by several males which is very stressful for them!), the other fish you already have not so much. Guppies and Mollies can cross breed so I wouldn't keep them together, but if you don't mind getting mixed offspring that's OK. The green spotted puffer is a sensitive fish that needs live feeding (snails, shrimp, small fish) and once it's mature it'll also start feeding on its tank mates (if it lives that long), so it's not a great “community tank” fish. AFAIK it's also only a fresh water fish during “childhood” (don't remember the correct term) and will need brackish water as an adult, and while Guppies and Mollies tolerate some salt I don't think you could keep them in brackish water. I wouldn't recommend keeping loaches (again, group fish that don't want to be kept alone!) together with a red-finned shark, s/he will become quite territorial once s/he's mature and attack the loaches (who can be quite agressive towards other bottom feeders, too). --Six words (talk) 09:22, 16 September 2012 (UTC)

Like Six words already mentioned, green spotted puffers are not the fish for beginners. And while sold as freshwater fish as juveniles, once they reach 2 to 4 inches they should be kept in brackish water, and as full adults (about 6 inches) they should be kept in marine water. They grow to six inches, are quite territorial. They will eat or otherwise aggressively attack and kill their tankmates as adults. They also need to be fed with live hard-shelled foods so their teeth can wear down naturally (e.g. crustaceans, clams, and snails), otherwise their teeth can become overgrown and they will starve. Bottom-line, you should not have bought one if you wanted a community aquarium. The same applies for the figure-8 puffer and almost all other puffers, all of which should be kept to one fish per 30 gallons of water. See if you can return the fish for its sake (DON'T release it local waterways).
For the rest of your fish, guppies are very good community tank fish, though the mollies not so much. Like other poeciliids, they are always trying to mate and can overpopulate very quickly. Males can become aggressive to each other and to other species, and should best be kept either as single-sex groups or in harems (one male to at least 2 or 3 females). Rainbow sharks are best kept to only one individual per tank. Once they're larger they may also start eating your smaller fish, so if I were you, I'd see if I could return it too.
For a community tank, this guide is excellent. A good general bit of advice is to plan ahead on what fish you want to keep and stick with it. Do not add more every time you see interesting fish in the petshop. Also take note of the mouth sizes. Don't keep fish together with fish that have mouths large enough to swallow the other. And always research how big the fish are going to be when fully grown. There's a good list of fish suited for community tanks here.
Stick with keeping only two to three species of the more peaceful and active schooling/shoaling fish for mid to upper-levels of the aquarium. Like cherry barbs, rainbowfish, harlequin rasboras, or white cloud minnows. Keep them in groups of at least six, and they more than make up for the lack of variety in species in small tanks as they are quite entertaining to look at moving around. Note that some rainbowfish species can grow quite large. A male/female pair of a single gourami species is also good as mid to upper-level fish. Either dwarf corydoras or otos are also better than your rainbow shark as bottom-tank dwellers. These should be kept in a group of at least 3 individuals, and otos may require a supplementary diet of boiled greens.-- OBSIDIANSOUL 12:34, 16 September 2012 (UTC)
Lepomis gibbosus, the beautiful Pumpkinseed Sunny.
My experience with gouramis is that they always end up killing each other and smaller fish like guppies. (They are also quite suicidal.) I don't recommend them, and certainly not with smaller fish. I never had a problem with guppies in groups of two males to one female, but I always only picked males with very fancy tails, so they were probably too slow to be too much of a problem--at least I never had a female die of harassment from a male. I was going to recommend trying to return the fish as the others have, but my experience is most stores won't take returns even if you don't want your money back. μηδείς (talk) 17:30, 16 September 2012 (UTC)
I meant the smaller gouramis, of course, given the earlier warning on mouth size - e.g. Trichogaster lalius, Trichogaster chuna, Trichopsis schalleri and Trichopsis pumila (which can only grow to a maximum of 1 to 3 inches). And yes, like other anabantoids (which include bettas), males are highly territorial with other males and will generally try to kill each other if kept together. And yes, larger gouramis are usually quite vicious. I've also kept wild-caught specimens of the much larger three-spot gouramis (which can grow up to 6 inches), and they are perhaps one of the most aggressive fish I've ever known. -- OBSIDIANSOUL 19:11, 16 September 2012 (UTC)
How does a fish commit suicide ? Do they jump out of the aquarium ? StuRat (talk) 17:58, 16 September 2012 (UTC)
Yes, the gouramis will deroofestrate themselves quite vigourously. (I suppose they'll defenestrate if your tank has windows.) Also, even the small mouthed ones will attack sick, wounded, or vulnerable fish, leading to their death within a few days. I never got gouramis after the first year or so of keeping a tank. Long after I started keeping a tank, a friend gave me a two-inch white gourami (I don't know the species). It was a monster. It killed half the fish in my tank within a week. I put it in a goldfish bowl by itself in the back yard. It froze over the winter. And lived. It finally committed suicide (Bugs?) having no othe victim to harass. After that I stuck with guppies in one tank and a beautiful pumpkinseed sunny I netted one summer in another. The sunny was my favorite ever, and lived three years. μηδείς (talk) 22:20, 16 September 2012 (UTC)
Hmm, I've been keeping a pair of lace gouramis for years, first with a swarm of cardinal tetras, now with a swarm of firehead tetras, some panda corydoras and amano shrimp. The only time one of the gouramis became agressive was when - after the female had died - I bought a new "female" that turned out to be male. Maybe I've just been lucky. --Six words (talk) 14:06, 17 September 2012 (UTC)
One thought, do they sell screen dividers, to keep the dangerous fish separate, yet still within the same aquarium ? (Of course, this won't solve the freshwater versus saltwater problem.) StuRat (talk) 17:58, 16 September 2012 (UTC)
Yes, they do sell dividers and isolaters for breeding but they are ugly, clunky, and get dirty over time. The OP would probably be better off getting a separate tank for the guppies, which according to gourami are probably the least ideal in their company. Tetras could go in either tank. The other fish should hold their own with the murdering gouramies. μηδείς (talk) 17:53, 18 September 2012 (UTC)

Analytical Ability/Reasoning questions[edit]

Dear Wiki Desk mates,

I am looking for an online resource/website/documents containing solved practice questions testing Analytical Reasoning questions (similar to the ones in Old GRE format). I am pasting out a sample question : SAMPLE QUESTION :

Six films (Quest to Hope, Rats, Sam, Terror, Victory, and Wellfleet are scheduled to be screened at a film festival. No more than two films may be screened during one day, but all of the films will be screened exactly once during the festival held Wednesday through Sunday. The screening schedule adheres to these parameters:

The producers of Terror will not allow it to be screened anytime prior to the screening of Victory. Rats and Sam are complementary shorts and are to be screened the same day. Quest to Hope and Wellfleet are both black-and-white films and should not be screened the same day.

Question 1 If Victory and Terror are screened the same day, which of the following must be true about the film festival schedule if it conforms to its parameters? (A) Quest to Hope and Wellfleet will be screened the same day. (B) Victory cannot be screened on Sunday. (C) Sam and Rats will not be screened the same day. (D) Exactly one day of the schedule will not have any film screening. (E) Each day of the schedule will have at least one film screening.


THANKS, Chris — Preceding unsigned comment added by (talk) 11:56, 16 September 2012 (UTC)

Do you just want resources, or do you also want our help solving those sample questions ? StuRat (talk) 17:52, 16 September 2012 (UTC)
This Google search on "analytical reasoning questions" brought up a wide variety of sites that host such questions and answers. Perhaps some of them will be what you are looking for. - Karenjc 18:45, 16 September 2012 (UTC)

@ Chris, I just want the resources--online, free and accessible, offcourse :-) @karenjc, I have been through this , the results on the first 4 pages are absolutely crap and insubstantial. I would be obliged , if you can help me with something more concrete.

Regards, Chris — Preceding unsigned comment added by (talk) 23:42, 16 September 2012 (UTC)

James D. Doss, my favorite mystery author, died in 2012. He lived in NM[edit]

and should be listed among the notable people in the Taos, NM, listing. Thank you. He was born in KY, don't know what city. — Preceding unsigned comment added by (talk) 16:17, 16 September 2012 (UTC)

The article James Doss already mentions his death. I have editied the Taos, New Mexico article to mention him and added an entry to the disambiguation page, Doss. As an aside, I have my doubts about some of the entries in Taos, New Mexico#Notable people - it seems some of them might have had only a fleeting association with the town. Astronaut (talk) 17:02, 16 September 2012 (UTC)
I have noticed the fleeting association phenomenon in many such articles. My solution is to clarify the length and period of association, since if you simply delete them they grow back. μηδείς (talk) 17:36, 16 September 2012 (UTC)

Why are Hiroshima and Nagasaki safe to live in now?[edit]

The surrounding areas of Chernobyl are still deserted and carry radioactivity warning. But why are Hiroshima and Nagasaki safe to live in now? Should there still be radioactive residue? Acceptable (talk) 18:23, 16 September 2012 (UTC)

There was just a lot less fallout in Hiroshima and Nagasaki than Chernobyl. The bombs were detonated very high above the ground and contained far fewer fission products than the Chernobyl accident. They're somewhat like comparing apples and oranges. A better comparison to Chernobyl would be something like Castle Bravo — a much larger bomb with much more fission products detonated at ground level. --Mr.98 (talk) 19:00, 16 September 2012 (UTC)
See Comparison of Chernobyl and other radioactivity releases#Chernobyl compared with an atomic bomb. One reason is that much more material was released during the Chernobyl incident than during Hiroshima/Nagasaki. (See [1] for a graphical depiction.) Another difference is the distribution of isotopes released. Hiroshima/Nagasaki was from a single atomic event by relatively pure uranium/plutonium. Chernobyl, however, was from a reactor core where the radioactive decay products had been sitting for a while under persistent neutron flux, leading to different isotope distributions. The final reason is simply time. It's only been 26 years since Chernobyl, but 67 years since Hiroshima/Nagasaki. Because of radioactive decay, even if they had started with the same amount of material, Hiroshima/Nagasaki would be less radioactive than Chernobyl, especially for those isotopes with a 2-40 year half life. And it's the short-half life isotopes that are usually the most concerning, as they're the ones emitting the most decay products in a given amount of time. (Although there are a number of longer-lived isotopes that are also a concern.) For example, this page [2] from the Hiroshima Peace Site notes that while the radiation was rather high for 24-48 hours after the blast, it rapidly decreased to normal background levels. -- (talk) 19:33, 16 September 2012 (UTC)
So Hiroshima and Nagasaki are safe to life in currently? How many years since the blast was it seemed safe it to live in? Acceptable (talk) 19:46, 16 September 2012 (UTC)
I don't think the cities were evacuated at all, although that may be more because the dangers of nuclear fallout weren't well understood rather than because it was actually safe. --Tango (talk) 21:51, 16 September 2012 (UTC)
It is true that fallout and residual radioactivity was very poorly understood. It's a bit more to the nub of it to point out that most of what we know about the effects of fallout and residual radioactivity on human populations — even today — comes from studying the survivors of Hiroshima and Nagasaki. The Atomic Bomb Casualty Commission and its successor, the Radiation Effects Research Foundation, have been studying the hibakusha now for many decades, and lots of things — including our current reactor radioactivity standards — are derived from this very key "data set." --Mr.98 (talk) 02:19, 17 September 2012 (UTC)
There is the fact that the greatest danger is from isoptopes with short radioactive half-lives, since they give off the most radiation most quickly, but also decay and become harmless most quickly. According to these sources, 80% of the residual radiation dissipated within one day, and the area quickly (within days) reverted to having no more than the normal background radiation of any average place on earth. μηδείς (talk) 22:03, 16 September 2012 (UTC)
That is the greatest acute danger (i.e. will give you radiation sickness), but not the greatest chronic danger (i.e. will give you cancer in a few decades). The chronic danger comes from the medium-length half-lives that are absorbed into bone marrow and do unpleasant things over the course of many decades (e.g. Sr-90, a "bone seeker" with a 29 year half life — long enough to be significant for human lifetimes, short enough to be a significant source of radiation in quantity), and also can get circulated quite broadly into the general ecological system. It's true that the acute radiation risk of atomic bombs is a rather short window (hence the idea of fallout shelters, which are meant just to house you for a few weeks when things are the "hottest"), but the contamination problem can be quite long-term. --Mr.98 (talk) 02:19, 17 September 2012 (UTC)
The cities did have relatively high rates of diseases that you would expect from the exposure to fission products with long half-lives — e.g. leukemia, birth defects, and so forth. The abstract of this study suggests that by the 1980s the rates were more or less what you'd find elsewhere. It should be noted that we are talking about increased risk factors here for what are still rare diseases; lots of cities have different cancer rates and different risk factors. --Mr.98 (talk) 02:19, 17 September 2012 (UTC)
Agree the mid-length isotopes are the most dangerous from ingestion, but our articles and what I have seen on the web imply there was little such fallout in the cities themselves, especially after the initial attack. In other words, the chance of ingesting Sr90 at ground zero itself within a few days after the attack was negligible. I am just repeating my understanding of what I have read above as a layman, so don't take it as an expert comment, so much as a question. μηδείς (talk) 03:59, 17 September 2012 (UTC)
The amount of mid-length fission products deposited into the soil of Hiroshima and Nagasaki has been a matter of controversy for many years, related to the fact that the US government at the time did want to downplay the fallout issue because it felt it would make it difficult to administer order in postwar Japan and because they feared, initially, it would create undue ambivalence among the American public with regard to the bombing.[3] I would not want to over-emphasize the contamination, but it was not zero. Again, the discussions I have seen suggest that the levels of certain associated cancers, particular leukemias, were elevated in the first generation or two after the bombs were dropped, but have dropped off. Even in their elevated state they were not extreme. --Mr.98 (talk) 12:49, 17 September 2012 (UTC)

Problem solving[edit]

For many years, my interest has been in finding a general problem-solving (equivalently, decision-making) algorithm. This is essentially entscheidungsproblem (and certainly at least a superset of it) and it has been shown that there is no general algorithm for solving it. My biggest problem at the moment is reducing the scope of this problem to one which is solvable. For instance, one may limit problems to solve to synthetic problems (such as physical ones), although even then the scope is too large since there are computational and other issues. Another approach to find an algorithm which gives approximate solutions, where the approximation is optimal in some sense. Does anyone have any advice? Widener (talk) 20:30, 16 September 2012 (UTC)

First, are you familiar with systems engineering ? This is an attempt to handle problems in a multi-discipline way, which seems to be what you are aiming for. StuRat (talk) 20:46, 16 September 2012 (UTC)
Also of interest might be Watson (computer), an attempt by IBM to answer any question. However, note that they gave up on having it think like a human, and settled for just doing a keyword search on terms they pull out of the question. StuRat (talk) 20:50, 16 September 2012 (UTC)
You'll have to at least reduce the problem to the point where it isn't turing-complete, which is how the original problem was proven unsolvable. I'm not sure how you would restrict it to "physical" problems, but even if you did many physical systems can simulate a turing machine. Using just a subset of the firts-order-logic you end up with problems like the Boolean satisfiability problem that are already pretty well-understood. I doubt you'll find a good definition for approximation - I can't see how you would have an approximate solution to the halting problem. (talk) 11:54, 17 September 2012 (UTC)
  • I suggest that you reduce your scope to solving the problem that you state here. Looie496 (talk) 18:30, 17 September 2012 (UTC)
smartass ( ̄ー ̄). Ssscienccce (talk) 19:03, 17 September 2012 (UTC)
WHAAOE, of course. See General Problem Solver and Soar (cognitive architecture). These systems solve problems in worlds described by states and rules. --Stephan Schulz (talk) 23:07, 18 September 2012 (UTC)