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A: The best advice I could give anyone is to be patient and to learn as much as you can about the hobby before you even buy a tank. Whatever you do, DO NOT purchase fish the same day that you set up their home... keeping fish healthy is not as simple as just giving them water and feeding them, but does not need to be extremely difficult either, if a few basics are followed. Please check and research the species of fish you want in the Fish.
A: This is really a matter of personal preference. Each filter has it's pluses and minuses, and different people will like different ones for different reasons. I'll break down what I think the strengths and weaknesses of basic filter types are (mainly depends on your tank size and what you want to keep in it), but this is often a matter of opinion:
Undergravel Filter (UGF)
A very low maintenance means of relatively natural filtration. The idea is to provide indirect water flow through the plates, as water displaces the air bubbles pumped in through the sides. The filter plates provide a large surface area which is kept oxygenated by constant flow, harboring large numbers of beneficial aerobic bacteria in the substrate itself. This is great in theory for slightly understocked tanks, and in my opinion, they are excellent for these purposes... however, in practice, many people keep either borderline or overstocked tanks. Since the UGF provides NO mechanical filtration (only biological), it should not be used alone for well-stocked tanks.
This is a filter, which again, only works by water displacement (air powered), not by a direct water pump, and so it too has no mechanical filtration capabilities, it only provides a large, aerated surface area for bacteria to grow and thrive. Best used as a supplement filter or a filter for a fry tank (since there is no danger of sucking up baby fish).
Hang-On-the-Back (HOB) Power Filters (i.e. Whisper, Penguin, etc.)
These are often the classic filters that most people think of, and come in a variety of shapes and sizes. They mostly work with a magnetic impeller which turns like a fan and pumps water through floss-covered filter plates, which can also contain carbon and other substrates (giving them both biological and mechanical filtration capabilities).
Some will also have a Bio-Wheel, an innovative and relatively new invention which allows for a separate area where "good" bacteria can grow, without having their entire populations dessimated every time the filter cartridge is changed. The advantages of the HOB power filters are mostly that the cartridges can be changed very easily for regular maintenance. Also, they come in a range of sizes to match different tanks, and are usually relatively inexpensive. Drawbacks include that they sometimes become clogged if regular maintenance and cleanings are not performed.
I would recommend them mostly for small to medium sized (5-50 gallon) tanks.
Canister Filter (i.e. Eheim, Fluval, etc.)
These filters are larger and a little more imposing to use. They are more expensive, but the advantages are that they can pump a large volume of water per minute, and so have both massive biological and mechanical filtration capabilities. They can also be used with a large assortment of media, most of which are highly porous (providing surface area for bacteria to grow). They don't need to be maintained as often as the HOB filter, but it's a trade-off, because when they do need to be cleaned out and have their media changed, it can be a project to work with the tubes and valves. Due to their high flow rates, they are not for smaller tanks, but will work very well in large tanks 40 gallons and up.
A: If you are a beginner, I'd advise you NOT to try and adjust your pH, especially not this way. pH up/down solutions are pure acids and bases, and often won't work, depending on your KH (buffering capacity or carbonate hardness). If your KH is high, then you are performing a very futile experiment (much like an acid/base titration, only with living creatures in the solution that don't react well to it) and if it is low, your pH will swing rapidly. It's the pH "bounce" that can stress and hurt fish, not really being kept steadily at the same pH. Many fish are amazingly adaptable if given time, but if their bodies are asked to do it quickly, they will either be stressed or go into rapid and life-threatening pH shock. I advise beginners not to mess with pH adjustment, and to try and match their FISH to the WATER (in other words, find out your pH first, and then buy fish that do well in that range), not vice versa. Also, there is no such thing as "perfect" pH, since different fish have different ranges of preference, and some are quite broad. 7.0 only means entirely neutral water, but this is not even necessarily the preference of many species, which may have ranges that center below or above neutral water, but cover a broad spectrum of tolerance. Trying to adjust pH can be necessary for the advanced breeder or keeper of hard-care species, but this should only be done by the experienced, and then with great care to watch all water parameters.
A: This is a controversial subject with fishkeepers.
A: This is most likely what's called a bacterial bloom. This usually happens when the nutrient content of your water is quite high, and the bacteria suddenly have a population explosion as a result. Don't panick, because this in itself is not necessarily something that will hurt your fish, but it is an indication of what your water values might be. This often occurs in relatively new tanks, which are not balanced places for fish to live. Check your ammonia and nitrite levels, and if you don't have a kit yet, I strongly suggest you buy one. Suddenly cloudy water can also sometimes be caused by overstocking, overfeeding, or a relatively sudden change in the water conditions of the tank. Usually, just keeping up with regular water changes will allow the bloom to burn itself out in a few days, but perpetual cloudiness can happen in tanks which are always overstocked. Doing very large water changes (>50%) can actually be counter-productive, in that they will feed the bloom and continue the vicious cycle by introduction of more nutrients. If the cloudiness has a green tint to it, it's very similiar, only the bloom is caused by algae. In addition to nitrogenous compounds of fish waste feeding it, organic phosphates will also contribute.
A: Goldfish produce more ammonia than other fish per unit mass because they are relatively inefficient eaters (in other words, they're basically poop machines). Ammonia is a toxic product of fish waste decay (you may have noticed that goldfish cloud water faster than many other species) that will quickly pollute Goldie's bowl and even frequent water changes will not be able to keep up with this. Not only will these wastes poison your fish directly, but they will stress them over time, reducing their natural immunity and making them more susceptible to disease. Smaller containers are inevitably more difficult to maintain balance in over time, and get dirtier faster, compounding this problem even more. Also, all varieties of goldfish grow to over six inches as adults (I've personally seen black moors and lionheads the size of small koi!). Some disreputable fish stores will try to convince you that they have different size varieties, but in truth, what this comes down to is age grades, since most fish are sold as juveniles. Chances are, if you buy a small goldfish, it will be a juvenile (grown specimens cost big $$!). If you see a goldfish that has bee n living in a container for more than a few years and it is only 2" long, it is severely stunted! All fish give off hormones and other compounds which limit their own growth in a closed environment, an adaptation that helps partition off limited natural resources in the wild.
Lastly, goldfish are a coldwater species, and thus evolved to need more oxygen per unit body mass than many tropical fish (more gases can dissolve in cold water than the same volume of warmer water). No bowl or small container will provide enough, even with an airstone! THE ONE INCH OF FISH PER GALLON GUIDELINE THAT APPLIES TO SMALL TROPICAL FISH CAN NOT BE APPLIED TO GOLDFISH. In fact, the consensus among many experienced goldfish owners is that they need a MINIMUM 10 GALLONS PER FISH. This is actually just a bare minimum for smaller specimens, and adults really should be given even more. This idea may sound shocking to many new to the hobby, some who may have even been told that"bowls are fine homes for goldfish" by pet store employees. The myth that they can live well in bowls is perpetuated largely by Western society and notions of convenience... and also by the fact that they are extremely hardy fish to begin with and can tolerate very suboptimal conditions in the short term, although these put them at great risk for stress and early death (their lifespan can easily be over a decade, if kept under good captive conditions!).
A: No! They are actually injected with fluorescent dye in an abusive process that hurts the fish and sometimes causes it to come down with serious diseases
A: These are most likely harmless nematodes (free living roundworms). They are relatively common in tanks that have a high nutrient content. The large majority of parasitic worms do not have an adult stage outside the fish host, and free-living nematodes are far more commonly seen than pathogenic (harmful) worms in tanks where fish are not fed live FW foods.
A: This is the characteristic presentation of a disease commonly known as "ich".
A: Building supply sources have lower standards for what what they make gravel out of, and different standards at that. The gravel they sell is usually in bulk, for the purpose of making cement or for landscaping uses; it is not meant to be submerged in water every day for years where animals have to live. It may contain many harmful substances, such as lime, calciferous rock, oxides, copper and heavy metal ores that can leach out into the water. In addition, if it is used for landscaping purposes, it may\line also be treated with pesticides. My advice would be not to risk it unless you are fairly familiar with that brand and the composition of the rock that the gravel is made of. There are brand name sands and gravels that are composed of silica, and if it \rquote s not too impure, it can be safe to use in almost any type of tank. Sands made of aragonite are not safe to use in the acidic to neutral freshwater tank (they will increase hardness), they are only ok to use in very hard water tanks (like an African tank) or marine tanks. They will have considerable buffering effects on the water.
A: With many freshwater tanks, the general answer is that it is not a good idea. Shells are composed of calcium carbonate, which will dissolve in soft to neutral water, the type of water many of our fish live in, gradually hardening it, as the ions go into solution. Many soft water fish, like neon tetras, for instance, will not react well to this. Shells and corals are safe to use in a hard water or marine setting, however, because the buffering capacity (KH) of the water is already quite high, and they won't dissolve at the same rate; when they do, the ions contributed are ones that the fish prefer in the water anyway.