Adult Tropical Hobbyist with a Single Tank.
One of the most common situations. Snoop around a little to see what equipment they have. Equipment they might need:
-pH/ammonia/nitrite test kits. These save fish lives, but too many people don’t buy them.
-spare heater
-fluorescent light bulb of correct size and shape. These do burn out.
-fluorescent light hood. Vastly better than incandescent.
-filter inserts for their particular filter
-frozen fish food
-aquarium salt. Useful medication for several diseases, and really cheap. Also good for a few species to have permenantly in their water.
-aquarium thermometer. Essential and extremely cheap.
-hospital/quarantine tank. 5 gal tank with heater and mechanical filter. It is really, really useful to be able to quarantine sick or newly acquired fish. Second hand tanks are a good way to find these cheap.
-general aquarium book

Child with A Single Small Unheated Aquarium
-fish tank decorations. Many children adore these and they are really easy to find in any petstore. They are often among the cheapest fishtank related gifts.
-a ten gallon kit. If the child shows real interest in their aquarium, get them decent equipment. A lot of the little plastic kits are nearly junk. If a plastick kit has goldfish in them, goldfish that live more than a year or so will outgrow the tank.
-a small filter. Many of these tanks don’t come with them and it really improves tank conditions and the ease of keeping fish.
-LED tank light. Looks pretty, uses little energy and now you can grow low-light live plants.

Adult with Single Cold Water Tank
-pH/ammonia/nitrite test kits. These save fish lives, but too many people don’t buy them.
-fluorescent light bulb of correct size and shape. These do burn out.
-fluorescent light hood. Vastly better than incandescent.
-filter inserts for their particular filter
-frozen fish food
-Aquarium salt. Useful for treatment of some diseases and very cheap.
-hospital/quarantine tank. 5 gal tank with mechanical filter. It is really, really useful to be able to quarantine sick or newly acquired fish. Second hand tanks are a good way to find these cheap.
-general aquarium book

The best gift here is probably a 10 gallon aquarium kit.  These usually come with everything required (though they often lack a heater) and are much better value for money than buying everything new separately.  Ten gallons is large enough to have a decent choice of species, yet small enough to keep costs down and be easy to find space for.   Five gallon kits are cheaper but they are much more restricted in terms of what you can keep in them.  If you have the money, 20 gallon kits allow a wider choice of species and decor, as well as increased stability in tank conditions which may make fishkeeping a little easier.

If you are short of money, check the web for second hand equipment.  Be careful to look over what you are buying carefully.  Remember that because it’s second hand, some of it may well be mismatched, missing or not work.  You may well end up buying the problem items new and this can raise the costs above what you initially estimated.  Been there, done that.  Even so, it can still be a lot cheaper than buying new.

Many people buy plastic kits that are cheaper than glass.  These are not such a good idea for a couple of reasons.  Most of these kits lack lighting, they scratch more easily and so don’t last as well, they don’t come with heaters, many heaters aren’t safe for use in them, and they may also lack a filter.  Many of them are also too small for anything other than a Betta or some shrimp.  If your budget is limited, I recommend second hand glass aquaria over these.

Another excellent gift is a book on aquarium keeping.  There’s a lot to aquarium keeping and having a decent book constantly on hand is a good way to prevent mishaps and respond to emergencies.

If the person you are buying for isn’t yet ready for fish, or isn’t sure that an aquarium is right for them, a book can give them a good idea of whether it is what they really want, and what type of aquarium would be best for them.

Don’ts when buying for new fishkeepers:

-Don’t buy the fish at the same time as the tank.  Get them after the aquarium has been set up for two weeks with plants in it, or fully cycled by another method.

-Don’t buy a goldfish bowl for a goldfish.  Goldfish bowls are far too small for a large, waste-producing fish like a goldfish.

-Don’t buy live animals immediately before Christmas.  The stores will be insanely busy and the salespeople won’t have time to help you as much as they normally would.  In bad cases, the animals may also not be as well looked after because the staff get overwhelmed.  Buy the tank, then go back and buy fish once the tank is set up and cycled.

-Don’t buy any pet you aren’t sure they want.

Here are some suggestions for groups of fishes that are compatible inhabitants for 5 gallon tanks.  I have only included fish is that are at least relatively easy to keep.

Note: I am assuming a standard 5 gallon long tank. If your 5 gallon tank is tall and narrow, it will support fewer fish as it is surface area that determines the number of fish you can have. There are a variety of rules of thumb people use for determining number of fish. For a properly-filtered tank of standard proportions containing tropical species, a 5 gallon tank should contain no more than 10 inches of fish. I have kept the fish inches here to 8.5 or less because this leaves more room for equipment malfunction such as short power outages and human error.

Cold water fish need more space – no more than one inch of fish per gallon in a standard-sized tank.

The tanks:
5 gallon tank with plants and a pH of between 6 to 7.

Fish Tank One: Amazon Nano Aquarium 1
6 Neon Tetras
1 Otocinclus

Fish Tank Two: Amazon Nano Aquarium 2
6 Black Phantom Tetras

Fish Tank Three: Betta Bachelor Pad
1 male Betta

Fish Tank Four: Lady Betta and Frogs
1 female betta
2 dwarf frogs
1 Otocinclus

5 gallon tank with a pH of 6.5 to 7.5

Fish Tank Five: Subtropical Stream
4-5 White Cloud Mountain Minnows

Fish Tank Six: Mini Catfish Tank
6 Pygmy Corydoras
1 Otocinlus

5 gallon tank with plants and a pH of 7.0  to 7.6

Fish Tank Seven: Where’s the Fish?
8 shrimp of any mix of species that doesn’t exceed one inch, Cherry shrimp is a good beginner species
1 horned nerite snail

Fish Tank Eight: Guppies, Guppies, Guppies
5 Male Guppies
1 horned nerite snail

They have their bad points too. They eat plants, poop a lot, and use space and oxygen you might have intended for your fish or shrimp. Snails can also act as an alternate host for some fish diseases, and for this reason you should never collect them from your local pond or lake.

The family Lymnaeidae is known as the pond snails. There are multiple species known as pond snails, and figuring out precisely which one you have in your aquarium may be more trouble than it’s worth. They are all hermaphroditic, and those seen in aquariums generally stay below 1 inch in length, although some seen in the wild can be nearly three inches.

Care and Feeding of Pond Snails:

They eat fishfood, algae, and soft leaved aquarium plants. They do not eat fish poop or have a noticeable effect on java ferns or java moss. Dissolved metals are often toxic to them, and fish medications based on metals, especially copper, should be avoided. Fish medications using dyes may also be toxic, although mine have survive Victoria Green B with no obvious ill effects. They prefer water that isn’t soft and acidic as they require calcium for shell formation. Mine is surviving in soft, acidic water, but its shell is showing signs of problems.

How to Avoid Pond Snail Overpopulation:

• Don’t overfeed. If they don’t have sufficient food, their population won’t explode.
• If you don’t want these snails, try picking over and quarantining plants before introducing them to the main tank.

How to Reduce Your Pond Snail Population:

• Put lettuce in a small container with the lid off. When snails collect in the container, remove it from the tank with the snails.
• Buy fish that like to eat snails. Puffer fishes, convict cichlids, certain african cichlids, clown loaches and yoyo loaches are sometimes recommended. But before you buy, check that the species you choose will fit in well with your other fish and not grow too large or require water conditions you can’t provide.
• Remove them by hand. If you have a lot, this will take a long time and you’ll never manage to get all of them.
• Use a snail killing chemical. However, chemicals that contain copper sulfate tend to be toxic to fish as well and need to be used with great care. You may prefer to use another method.

Sources:

How to Get Rid of Small Snails

Pond Snails, Bane or Boon?

Ryan Wood. Pond Snail. Planet Inverts.

The Living World of Molluscs. Pond Snails Lymnaeidae

Shrimp tolerate a wide variety of temperatures but temperature tolerances vary between species. Most will tolerate normal tropical aquarium temperatures, but some require higher temperatures and others are quite happy at temperatures lower than most tropical fish will stand.

Because shrimp keeping is a young part of the aquarium hobby, estimates of what temperatures a specific species like vary between sources. For example, the Amano shrimp is a common, well known shrimp in the hobby. Planet Inverts gives a temperature range for this species of 68-82F, while shrimpfanatics gives a range of 10-28C (50-82F) and most books on the aquarium hobby have no detailed information on aquarium shrimp at all! It is also noticeable that different captive-bred color varieties of the same species are sometimes given as having different temperature ranges. This is possible if the color varieties came from different areas or were kept under different captive conditions for long periods of time, but it is not very likely. It makes me suspicious of the information’s accuracy.

What can one do in such a situation? Pick what seems the most likely estimate for the shrimp you wish to keep. This is usually the parts of the range that overlap between sources. In the case of the Amano shrimp, that would be 68-82F. Watch your shrimp. Are they dying? Are they eating enthusiastically? Are they breeding? Adjust temperatures until your shrimp show the full range of healthy behaviors. Once you have this information, put your results up on the net and let other people know. In an area of the hobby this new, we all have the ability to add to what is known.

For those of you trying to pick a shrimp species, here are temperature ranges for shrimp with non-standard temperature tolerances. All information here is from Planet Inverts.

Aquarium shrimp that tolerate cool water (minimum less than 70F):

Amano Shrimp Caridina multidentata 68-82F
Bee Shrimp Caridina cantonensis “Bee” 64-78F
Caridina cantonensis “blue tiger” 69-81F
Caridina cantonensis “crystal red” 64-78F
Dark Green Shrimp Caridina sp. “Dark Green” 68-82F
Glass/Grass Shrimp Palaemonetes paludosus 64-85F
Golden Bee Shrimp Caridina cantonensis “Golden Bee” 64-78F
Neocaridina heteropoda 64-82F
Orange Bee Shrimp Caridina cantonensis “Orange Bee” 69-81F
Red Cherry Shrimp Neocaridina heteropoda “red” 64-82F
Red Tiger Shrimp Caridina cantonensis “Red Tiger” 59-81F
Snowball Shrimp Neocaridina cf. Zhanjiajiensis var. “white” 69-82F
Tiger Shrimp Caridina cantonensis 59-81F
Caridina cantonensis “white bee” 64-78F

Shrimp that require high temperatures (minimum 75F and up)

Brown Camo Shrimp Caridina sp. “Brown Camo” 78-85F
Cardinal Shrimp Caridina sp. “Cardinal” 78-85F
Harlequin Shrimp Caridina cf. spongicola “Harlequin” 78-85F
Orange Delight Shrimp Caridina sp. “Orange delight” 78-85F
Red Goldflake Shrimp Caridina sp. “Goldflake” 78-85F
Sulawesi Shrimp Sp. name not given, new intro. 80-82F

Sources:

Planet Inverts

Shrimpfanatics

Freshwater Shrimp

Freshwater shrimp are probably the most decorative freshwater invertebrates.  There are many species, each with its own color pattern and mode of life.  As most species are small, they do not require much space. Freshwater shrimp are harassed or eaten by many fish species so tank mates must be considered carefully.  I tried keeping Cherry Shrimp with a Pygmy Gourami and regretted the decision. The Gourami harassed my shrimp and probably caused the death of two of the five.   Endler’s Livebearers, however, coexisted peacefully with the shrimp.

Different species have different temperature and pH tolerances, but some of them, like the Amano shrimp, tolerate cool water very well.  The Amano shrimp requires brackish water to breed, which makes it very difficult to breed in captivity.  Individuals in pet shops can be assumed to be wild caught.   Red Cherry shrimp prefer tropical temperatures but have a tolerance for a wide pH Range and can be easily bred in captivity.   They are easy to find and are recommended for beginners.

There are so many different species of freshwater shrimp with so many different needs that it is hard to make generalizations.  Detailed information on the different species of shrimp and their care can be found at http://shrimpfanatics.com/.

Crayfish

Crayfish live in running water in nature.   This means they need a filter or at least an air stone.  They are are best kept one to a tank as they are likely to fight with each other.   Crayfish are larger than most of the other invertebrates we are discussing here and large adults will need considerable space.  Ten gallons is enough for an adult of most of the North American species, but some of the Australian species can reach 16 inches and would need a 30-50 gallon tank.  There are a few dwarf species such as the Dwarf Cajun Crayfish, Cambarellus schufeldtii, that can be kept in a smaller tank or in a group in a 10 gallon tank if there are enough hiding places.

Crayfish will eat fish if the fish are small enough, so tank mates need to be considered very carefully.  Crayfish can be fed on shrimp pellets, but there are often specialty crayfish foods available.  Temperature requirements vary, but many species are happier in cold water than a tropical tank.  More information can be found at canadiancrayfish.com.

Triops

There are two Triops species commonly kept in captivity, T. cancriformis and T. longicaudatus.  Both have similar care requirements.  Triops prefer warm water of about 22-31° C.  They do not require much space.  One Triops can easily be kept in a gallon container.   They are typically bought as dried eggs which are sent through the mail without harm.  The eggs must dry out, otherwise they will not hatch.  They prefer a neutral to alkaline pH.   A filter is not required, but they produce enough waste that a weekly 25% water change is recommended if you aren’t using a filter.  They will eat almost anything.  More information about Triops can be found at mytriops.com

Snails

While people often try to get rid of snails in their aquarium, snails can be a fascinating addition if you get the right species.  Any animal can be a pest if it’s in the wrong place.

Snails do not eat fish poop.   They usually eat uneaten fishfood, algae, and some aquarium plants.   The last is the reason why they are often unwelcome in planted fish tanks.  Snails require a certain amount of calcium in the water to build their shells, and for this reason tend to do better in hard alkaline water than in very soft acidic water.

Apple snails grow large and eat plants.  They are sold under a variety of names, including Golden Mystery Snail, Ivory Snail, Mystery Snail, and Giant Ramshorn.   There are multiple species, one of which, Pomacea maculata, is the world’s largest freshwater snail.  It can grow up to a diameter of 6 inches.  Because of its size it is not really suitable for bowls or small tanks.  More information on apple snails can be found at applesnail.net.

Malaysian trumpet snails burrow in the gravel and eat uneaten fishfood.   They do not eat plants.  They have an unusual elongated shell that makes them easy to recognize.  More information can be found at planet inverts.

Common pond snails are the snails that turn up unintentionally when you buy aquatic plants.   They breed prolifically, and are often considered a pest.  I currently have a couple in my aquarium and they appear to be doing no harm, but that may be because the plants in my tank are things like java fern which are avoided by most plant eaters.  The pH is low enough that it may be inhibiting them as well.  These snails are easy to feed, do well at both tropical and low temperatures and are not aggressive towards other animals so in the right place they can be good tank inhabitants.

There are a number of snail species around in addition to those above.  Knowing the habits of the species you pick will go a long way to making you happy with your snails.

In the End

There are many interesting invertebrates that can be kept in freshwater tanks.  Each type of invertebrates has its own needs and habits which should think consider as you would for any fish that you decided to add to your tank.  When treated with respect, freshwater invertebrates can be great tank inhabitants.

Goldfish, Carassius auratus: Superb in Large Unheated Aquariums

Goldfish grow.  Common goldfish can grow up to approximately 12 inches in length which is larger than some of the containers the juveniles are kept in.  They also produce a good deal of waste as they grow.   Fancy varieties usually stay smaller than common goldfish, but their fancy fins are inclined to develop finrot in dirty water.  This makes the lack of a filter problematic.  Goldfish are cold water fish so the lack of a heater is perfectly fine.

In short, they are ideal for a large unheated aquarium with filtration but are not suitable for a bowl.

White Cloud Mountain Minnow, Tanichthys albonubes: Good for Small Unheated Aquariums and Large Bowls

White cloud mountain minnows prefer lower temperatures than most tropical fish and for this reason they are often kept in unheated aquaria.   Their natural temperatures are 64-71F.  They are very small fish, staying under two inches in length.  However, they do school so is important to provide enough space for at least a couple of fish, preferably more. Fortunately their small size means that two or three can be kept comfortably in a 2 or 3 gallon aquarium. Of all the fish discussed here, these are probably the best for a large unheated bowl or small unheated aquarium.

Zebra Danio, Brachydanio rerio: Not Ideal

Most danios are small, the zebra danio being 1¾ inches in length, and they are tolerant of a wide range of temperatures.  Their natural temperature range is 64-75F.  However, they are fast swimmers and like to school which makes keeping them in a tiny aquarium questionable.

Watching a school of these fish in a large tank is a completely different experience from watching one or two in a tiny tank.  In a large tank they can get up speed and they seem to fly through the water in a group.  It is beautiful, but it is something you will never see if you put these fish in a betta cube.

Betta, Betta splendens: Ideal for Small Heated Aquariums or Bowls

Bettas stay small, usually growing to approximately 3 inches in length.   The waters from which they come are naturally rather stagnant and they have the ability to take in oxygen from the air.  This greatly increases their resistance to foul water.  They dislike fast filtration.  They are solitary in temperament and swim slowly.  This makes them seem like an ideal candidate for the small unfiltered bowl.

However, the waters from which they come are warm: the average temperature is 24-30C (75-86F), according to Fishbase.org.  While they will survive in an unheated bowl provided the room is decently warm, keeping them in an unheated aquarium seems questionable.

Some of the object in which Bettas are kept are too small for any fish.  They should have room to turn around easily and room to spread those magnificent fins of theirs.  Keeping these fish in an adequate sized and warm tank has advantages to the fishkeeper in addition to feeling good about the way you keep your fish.  Healthy fish display more, build bubble nests and check every nook and cranny of the aquarium for missed food.  They are much more interesting to watch, and a betta doing an aggressive display in a well lit aquarium is a truly stunning sight.

It doesn’t take that much effort to set up a small aquarium with a heater, and this fish will reward you well if you do.  Secondhand equipment can often be bought for less than new equipment and a 2 gallon aquarium is more than enough space for a Betta.

Least Killifish, Heterandria formosa: Ideal for Small Aquariums or Bowls

This is a very small fish native to North America which is related to the guppy.  The Males are extremely small at 3/4 inches, and they prefer normal tropical tank temperatures of 68-78F.  Their small size and tolerance of moderate temperatures makes them ideal for a small unfiltered aquarium, provided it is not subjected to cold temperatures.   The largest problem with these fish is likely to be finding them, since they are not common in aquarium stores.

Invertebrates: Better Than Fish for a Bowl

Freshwater invertebrates may work well in truly tiny tanks if you do not wish to keep fish.  Freshwater shrimp are harassed by many fish species and may do better on their own.  There are also many species of snail, and a shrimp-like creature known as Triops.  Different species have different temperature tolerances, but some of them tolerate cool water very well.  You could also try brine shrimp if you are willing to handle very salty water.

Note

All temperature information is taken from fishbase.org, and are the temperatures at which the fish have been found living in the wild.  Some species can tolerate wider ranges.

Types of Plant Lights

The most common aquarium lighting is the normal output, or standard, fluorescent. Standard fluorescents come in many different spectra. Some are optimized for plant growth, and are sold as plant lights in pet stores and garden shops. These produce less intense light than metal halide, Very High Output (VHO), or T5 fluorescents, but the color spectrum produced is still designed to encourage healthy plant growth. People often use one, two, three, or four of these tubes together to light a tank brilliantly enough to suit the plants they wish to keep.

VHO fluorescents and T5 fluorescents are much brighter than standard fluorescents. They are most commonly used in reef tanks and planted freshwater aquaria.

Metal halide lighting can be used in planted freshwater aquaria, but its main use is lighting reef tanks. It is expensive and the extremely high light levels it produces are not necessary for the vast majority of freshwater planted aquaria.  It may well be useful in very deep tanks in which live plants grow.

LED lights intended for use as plant lights can be found on the Internet here. Given the efficiency of LEDs, this form of lighting will likely become much more common in the future. As with any new technology, the early versions sometimes have problems.

Low Light Plants and Standard White Fluorescent Lighting

There are certain plants that will do well even in the absence of special plant lights and high light levels. These include Java Fern, Microsorium pteropus, Java moss, Vesicularia dubyana, and Crystalwort, Riccia fluitans, among others. Many plants will grow under standard white fluorescent lighting so long as there is enough light, but you will get better growth under plant lights.

Sunlight

Contrary to popular wisdom, a small amount of sunlight over a short period of time may do no harm and significantly improve plant growth. The reason sunlight has a bad reputation is because too much sun will cause a tank to overheat. This can kill both fish and plants.

The best plant growth I ever had occurred when I sat my 7 gallon tank near a north-facing window where it got a small amount of sun during the early morning. For artificial lighting the tank had one compact fluorescent light bulb. My main plant problems with that tank was too much green algae, and a water lily that would not grow because I kept digging up the bulb when I cleaned the tank.

In conclusion, when picking lighting for your planted tank, you need to consider the types of plants you wish to keep and the depth of the tank.  Deep aquariums need stronger lighting than shallow ones, and light requirements vary among plant species.  At least there are many options for you to choose from.

Many aquarium filters use all three types of filtration to clean the water, while others may use two or even one. A simple corner box filter performs all three functions and can be used as an example. The filter consists of a box containing a layer of activated carbon and a larger layer of filter wool. The filter wool is not actually wool, but is usually made of polyester batting.

 Air enters through a tube that opens at the bottom of the box. The air bubbles rise through the layer of activated carbon and then through the filter wool before leaving through the holes in the top of the box. Because the air moves through the water, the movement of the air causes the water to move upwards through the filter.

The water carries with it chemicals and particulate matter. The activated carbon adsorbs some of the chemicals (Lenntech), which removes them from the water, while the filter wool traps some of the solid particles. On the filter wool live bacteria that convert ammonia into nitrite, and other bacteria that convert nitrite into nitrate. These bacteria are aerobic, which means that they require oxygen. The movement of the water allows oxygen to reach them easily and provides a constant stream of water containing the ammonia to be converted.

The box filter described here is one of the cheapest and simplest filters available. They work very well in small tanks, but other types of filters are more common in larger tanks.

References:

Lenntech Water treatment & air purification Holding B.V. Retrieved March 3, 2009
http://www.lenntech.com/adsorption.htm

In the wild it is threatened by habitat destruction (Ekaratne, 2000). The cherry barb lives in forest streams in Sri Lanka and much of Sri Lanka has been deforested. There are also problems with introduced fish species in Sri Lankan freshwater habitats (Ekaratne, 2000), although I am not sure if the cherry barb is affected by this directly. The IUCN lists the Cherry Barb as being lower risk but conservation dependent. This means that it would be listed as vulnerable except that there are programs in place to protect it (Pethiyagoda, 1996). It was listed as vulnerable prior to the conservation initiatives being implemented. However, its status has not been updated since 1996, which makes it difficult to determine how well the fish is doing now.

According to fishbase.org, some especially colorful varieties may be being overfished for the aquarium trade, although some of the cherry barbs exported from Sri Lanka are hatchery bred (Ekaratne, 2000). The Cherry barb is present in the Sinharaja forest reserve, which is the last large area of primary tropical rainforest on the island. The status of this reserve as the largest on the island is rather startling to me, as it is only 21x4km in extent (Sinharaja forest reserve). Still, the cherry barb is a very small schooling fish so it may be big enough to preserve the species provided that the fish are efficiently protected within the park. The protection of the specific especially colorful varieties is another question.

 Overall, I would probably avoid buying wild caught cherry barbs but there’s certainly no problem with buying the captive bred ones.  Of course, telling the origin of the fish is difficult when most pet shop workers do not necessarily know where the fish come from.  This is a standard problem with the aquarium hobby for far too many species.

References:

Ekaratne, S. 2000. A Review of the status and trends of exported ornamental fish resources and their habitats in Sri Lanka. Published by Y.S. YADAVA for the Bay of Bengal Programme. ftp://ftp.fao.org/docrep/fao/007/ad920e/ad920e00.pdf

Fishbase.org. Retrieved 27 February 2009.http://www.fishbase.org/Summary/SpeciesSummary.php?id=6147

Pethiyagoda, R. 1996. Puntius titteya. In: IUCN 2008.2008 IUCN Red List of Threatened Species. <www.iucnredlist.org>. Retrieved 27 February 2009.

Sinharaja forest reserve. World heritage sites. United Nations environment programme and the world conservation union monitoring center. Appears to have been written post-2003. Retrieved 27 February 2009. http://www.unep-wcmc.org/sites/wh/pdf/Sinharaja.pdf