Many of the tropical fish seen in pet stores are not fully grown. The final size of the fish varies dramatically between species. This is a list of the sizes that individual species are likely to grow to. Only some species are listed here, and adult fish of the same species vary somewhat in size. This is meant as a general guide to avoid buying fishes that will outgrow your tank.

Some of these species are sometimes illegally wild-caught and exported from their countries of origin; just because it is on this list is not a recommendation for keeping it.

Enormous Tropical Aquarium Fishes (Over 16 in.)

Red Tail Catfish: Phractocephalus hemioliopterus
Arapaima, Pirarucu: Arapaima gigas (potentially to 16 ft. usually less)
Arowana: Osteoglossum bicirrosum, Osteoglossum vandelli
Black Arowana: Osteoglossum ferreirai
Asian Arowana/Green Arowana: Scleropages formosus
Australian Arowana: Scleropages jardini
African Arowana: Heterotis niloticus
Tiger Shovelnose Catfish: Pseudoplatystoma fasciatum
Shovelnose Catfish: Sorubim lima
Reticulated Pimelodid: Perrunichthys perruno
Plecostamus, Pleco, Suckermouth Catfish: Hypostomus plecostomus
Snow King Plecostomus: Liposarcus anisitsi
Blue-eyed Panaque, Blue-eyed Plecostamus: Panaque suttoni
Sailfin Plecostamus: Pterygoplichthys gibbiceps
Walking Catfish, Albino clarias: Clarias batrachus
Fire Eel: Mastacembelus erythrotaenia
Ornate bichir: Polypterus ornatipinnis
Knife Fish; Featherback: Notopterus chitala
Mozambique Mouthbrooder: Oreochromis mossambicus
Gourami: Osphronemus goramy
Black Shark: Labeo chrysophekadion

Sources:

Butler, Rhett A. 1999-2008. Mongabay.com – San Francisco, CA

Practical fish keeping http://www.practicalfishkeeping.co.uk/pfk/pages/home.php

Mills, D. 1987 Illustrated Guide to Aquarium Fishes. Galaxy Press, England

Many popular aquarium fishes come from the Amazon Basin. These fish include tetras, corydoras catfishes, suckermouth catfishes, dwarf cichlids, discus, piranhas and many others. Some of these species arrive in our fish tanks after being captive bred in many places around the world, but many others are wild caught and some are new imports that have only just been discovered. There are almost certainly more species that have not been discovered yet. What are the effects of climate change and deforestation in the Amazon on wild fish?

Effects on the Amazon

The combined effects of deforestation and climate change are likely to result in significant drying of the Amazon Basin as well as disappearance of half or more of the forest, possibly within the next 20 years (Nepstad et al, 2008). The reasons for the drying are twofold: cutting the forest reduces the ability of the forest to create its own climate, and the warming climate means increased evaporation and more fires. The increased rate of fire reduces the area of forest further, making the situation worse. Loss of the Amazon rainforest would also accelerate climate change by removing one of the world’s most important carbon sinks.

Potentially, deforesting a large part of the Amazon, when combined with climate change is likely to result in a Savannah type ecosystem with much less water over most of the area now covered by the Amazon rain forest. Some models predict the loss of the Amazon from climate change even without deforestation (Harris et al, 2008). These changes are likely to be very difficult to reverse, and drying of the forest has already been observed (Li et al., 2008).

Effects on Fish

Put together, this means fewer streams in which fish can live and breed. Smaller streams will likely disappear entirely while water levels are lowered in larger streams and lakes. A possible preview of some of the effects might be the 2005 Amazonian drought. This drought was primarily caused by unusually warm sea surface temperatures in the tropical north Atlantic. In 2005, streams disappeared and lower water levels in larger streams and lakes caused fish kills as well as increased fire (Marengo et al, 2008).

If these changes occur as predicted by current models, the area of habitat available to the fish species that depend on the forest will be vastly reduced, and many species will probably go extinct. Those that don’t will be scarcer they are now and will need to be bred in captivity if they are to continue appearing in hobbyist’s fish tanks. Considering how many aquarium fish species come from the Amazon, this is likely to have a major impact on the hobby.

What Can We Do?

This is not a scenario likely to be attractive to most fish keepers, but there are things that can be done to make the situation less devastating. The two key variables are climate change and deforestation in the Amazon basin. Therefore, all the usual methods of reducing climate change apply. Information on how to reduce climate change, and links to other informative sites, can be found here, and at many, many other sites on the Internet.

Reducing deforestation in the Amazon is a little more tricky for those of us who do not live in South America. More about the problems plaguing the Amazon, as well as possible solutions to these problems, can be found here.

References:

Harris, P. Huntingford, C., Cox, P. (2008) Amazon Basin Climate under global warming: the role of the sea surface temperature. Philosophical Transactions of the Royal Society 363: 1753-1759

Li, W., Fu, R., Robinson, I., Juarez R., Fernandez, K. (2008) Observed Change of the standardized precipitation index, its potential cause and implications to future climate change in the Amazon region. Philosophical Transactions of the Royal Society 363, 1767-1772.

Marengo, J., Nobre, C., Tomasella, J., Cardoso, M., and Oyama, M. (2008) Hydro-climatic and ecological behavior of the drought of Amazonia in 2005 Philosophical Transactions of the Royal Society 363,1773-1778

Nepstad, D., Stickler, C., Soeres-Filko, B., Merry, F. (2008) Interactions among Amazon land use, forests and climate: prospects for a near term forest tipping point. Philosophical Transactions of the Royal Society 363, 1737-1746

Lighting for plant growth is rather a specialized topic. Most plants need quite bright light to grow properly. Because water absorbs light much more quickly than air does, a deep tank needs a lot of lighting if you want to grow plants.

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.

The cherry barb, Puntius titteya, is a common aquarium fish that is an easily spawned egg layer. The fry are somewhat hard to rear as they require extremely small food and protection from their parents, but when these needs are met they do very well. This is a description of my experiences in spawning and rearing cherry barbs.

My first male and female began courting the evening I took them home from the pet shop. They began spawning the following morning, and did so frequently after this. The male was extremely assiduous in courting the female, and would not stop chasing her around the tank. I went back and bought a second female in order to give the first some peace, and then started adding other fish species to the tank. Fry did not survive in the community tank.

In order to raise fry, I moved the cherry barbs to a 5 gallon tank containing Java moss and Java ferns. I did not succeed in raising any fry from the first spawnings due to an inadequate food supply. It was the middle of winter; all green water sources were frozen and I could not buy any food aimed at egglayer fry in the local pet store. When I tried again later, the weather had warmed and I had also taken to creating green water indoors which gave me a food source for the young fish. I only succeeded in raising one fish the first time, but the fish was a healthy female. I believe the scarcity of offspring in this case may have been due to a poor spawning.

I later left the three fish together in the 5 gallon tank. I had not intended to raise any offspring, but when I looked inside a jar of dirty fish tank water I was about to pour on my houseplants I discovered a young fish swimming inside. I then moved the adults to the main tank and proceeded to add green water 2 to 3 times a day to the little tank, graduating to egg yolks squished through nylon stocking and crushed flake food as the fry grew. Some 40 or so young fish from that spawning survived.

While cherry barbs have a reputation for being shy and rather timid fish, I found that this was untrue of the male so long as there were both females and hiding places around. Under these circumstances the male spent the majority of his time displaying and chasing the females. He was in fact the most aggressive fish in the tank, chasing my neon tetras and occasionally attempting to chase the corydoras catfish which were larger than he was. They ignored him, but his harassment of the female Cherry barbs appeared to cause them stress. One developed a fungus patch on her side which disappeared after I separated her from the male, and one female jumped out of the 5 gallon tank with fatal results. I believe she did this in an attempt to escape the male’s attentions, and any future breeding of cherry barbs will be done with a cover on the tank.

The male’s aggressiveness in this regard severely surprised me as nothing I had read about this species suggested this level of aggression. It is notable that his aggressiveness only occurred when females were present; in the absence of females he usually hid in the darker corners of the tank.

Fry have a reputation for being sucked into filter intakes. The question is, how does this occur and is it actually a problem?

The most often recommended type of filter for the fry tank is the sponge filter. This type of filter works by pulling water through the sponge. The holes in the sponge are small enough and the water current is weak enough that fry and eggs are unharmed and cannot be pulled inside. The microorganisms growing on the sponge are also considered to be a source of food for fry. This makes these filters doubly valuable in the fry tank.

When rearing fry I used a box filter since it was what I happened to have handy. Fry got into the filter, but they seemed completely unharmed by the experience, being healthy and about the same size as fry living outside the filter. I merely check for fry when I clean the filter and move any that I find into the main tank.

Undergravel filters should not pose a problem in drawing fry into themselves as water intake occurs through the gravel bed. I suppose it is potentially possible that eggs could get sucked down and any resulting fry be stuck in the gravel bed, but I could not say if or how often this happens.

I suspect the main complaints about fry being sucked into filters involve power filters where there is quite a strong a current to draw fry into the intake tube. The danger to fry could be reduced by placing something over the filter intake that has very small holes – such as a piece of nylon ladies stocking attached with an elastic band. The holes should be too small for the fry to be sucked through into the filter. However, if current at the intake is extremely strong the filter could still potentially harm the fry by holding them against the nylon stocking by a current of water too strong for them to swim against. I have no personal experience using this sort of filter with fry, but based on other people’s comments I would not recommend it.

Sponge filters are usually very cheap to buy so you may find the best solution for a fry rearing tank is to buy one of them and leave the power filters for tanks with adult fish. A simple sponge filter may cost around $5-10 CAN, or it is possible to make your own. However, in addition to the filter you will also need plastic tubing and an air pump. An air pump for a small tank is usually under $20.00 CAN, but you may already have one so check before buying. With a little extra tubing and valves you can often hook more than one thing up to the same air pump.

In short, fry getting into the filter is only a problem with certain filter types. With box, undergravel, or sponge filters fry either won’t enter the filter, or are unlikely to be harmed if they do.

This small barb comes originally from Sri Lanka and is a popular fish in the aquarium hobby. It is designated as low vulnerability conservation dependent by the IUCN, which means that there are some conservation programs in place to protect it without which it would be considered vulnerable (Pethiyagoda, 1996). There are some indications that the most brightly colored population may be being reduced in number by export for the aquarium trade (fishbase.org). Overall, this situation is very similar to that of the cherry barb, Puntius tittaya, which lives in many of the same habitats in Sri Lanka. Both fish are present in the Sinharaja forest reserve (Sinharaja forest reserve).

The black ruby barb is bred in captivity in Sri Lanka as well as being wild caught for export (Ekaratne, 2000). It is also bred in hobbyist’s tanks and instructions for breeding can be found in such places as Mongabay.com. I am not certain to what extent it is bred commercially outside of Sri Lanka.

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

Butler, R. San Francisco, CA Mongabay.com. 1999-2008. Retrieved 09 March 2009 http://fish.mongabay.com/species/Puntius_nigrofasciatus.html

Pethiyagoda, R. 1996. Puntius nigrofsciatus. In: IUCN 2008. 2008 IUCN Red List of Threatened Species.www.iucnredlist.org. Downloaded on 03 March 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 4 March 2009.

http://www.unep-wcmc.org/sites/wh/pdf/Sinharaja.pdf

There are three main types of filtration: mechanical, biological and chemical. Mechanical filtration removes particles from the water by forcing the water through a medium with holes. Particles larger than the holes get stuck in the filter and are removed from the tank. Biological filtration uses bacteria to transform ammonia into less toxic substances. Chemical filtration usually involves the use of activated carbon to remove chemical substances from the water. There are also certain specialized methods of changing the water’s chemical makeup such as reverse osmosis, protein skimming and peat filtration. However, these are special cases that are not used or required for the vast majority of freshwater tanks.

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

The Cherry Barb originally comes from Sri Lanka. It is very common in the aquarium trade, as it is hardy, easy to breed, peaceful, small and quite pretty. The vast majority of individuals seen in pet stores are captive bred.

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

When keeping fish, you use water. There is no way to avoid it, but there are plenty of ways to make the most of the water you do use. Dirty aquarium water can be used to water plants, the aquarium can be covered to lower evaporation, filtration systems can be used to remove particulate matter and convert ammonia to less toxic nitrate, and live plants can be used to convert some of the nitrate into living plant tissue. These methods can be used together to reduce the water use of the tank and to raise the quality of life for your fish.

Dirty fish tank water is very good for plants. Because it contains fish waste, it also acts as fertilizer. When I do a water change, I use the dirty water to water any plants that are dry. Using aquarium water as the main water source for my plants, I have successfully grown many types of houseplants using no other fertilizer. The houseplants are healthy enough that they keep growing outgrowing their pots, yet there are no signs of fertilizer burns. The one caveat to using dirty fish tank water is that it is possible it may contain salmonella (Senanayke et al., 2004), and so it should not be used on vegetables that the water will touch directly. Water from the fish tank can be placed in a separate container so that it can be used at times other than when you’ve just done a water change.

An aquarium cover serves two purposes: it serves to lower evaporation, and to reduce the risk of fish jumping out of the tank. Many fish species will jump occasionally, and a jump out of the tank onto the floor is usually fatal for the fish. Tanks should never be completely (airtight) covered as gas exchange occurs at the water’s surface that provides oxygen for the fish to breathe, but a hood over a fish tank certainly seems to do no harm. I’ve noticed that fish tanks with hoods have less water evaporation, presumably because the water vapor recondenses on the cover and runs back into the tank.

Most fish tanks these days seem to have filters. Since filters increase the number of fish you can keep comfortably in a tank of a given size, or if you keep the number of fish the same reduces the number of water changes you have to make, it is not surprising that filters are so popular. I doubt most people are thinking of water savings when buying a filter, but the benefit exists. Biological filters transform ammonia into nitrite and then into nitrate through the actions of bacteria.

Live plants use the nitrate that is produced by the filter as a nitrogen source. This means that some of your gradually accumulating toxins will be transformed into living plants which will beautify your tank. However, this will only occur in useful amounts if your plants have sufficient light for proper growth.

No matter how many live plants you have, and how good your filtration is, you still need to do regular partial water changes. Having these things simply means that know you won’t be depending on water changes alone to keep metabolic poisons to a minimum.

Overall, a small fish tank really doesn’t use very much water compared to many of the other things people do. It is only when we get into very large fish tanks or multiple fish tanks that water use becomes an issue for those of us who don’t live in areas with severe water shortages. Still, one might as well use resources efficiently.

References:

Senanayake, S., Ferson, M., Botham, S. Belinfante, R. (2004) A child with Salmonella enterica serotype Paratyphi B infection aquired from a fish tank. Letters. Medical Journal of Australia.

Africa
Ammannia gracilis: tropical Africa
Anubias barteri: tropical West Africa
Aponogeton ulvaceus: Madagascar Paso
Bolbitis heudelotii: Ethiopia to South Africa
Ceratophyllum demersum (hornwort): worldwide
Ceratopteris thalictroides (oriental water fern): tropics, worldwide
Crinum natans: Africa
Nymphaea lotus(Egyptian waterlily): East Africa, Madagascar, Southeast Asia
Riccia fluitans (crystalwort): worldwide
Vallisneria spiralis (corkscrew Vallisneria): tropics and subtropicsIndian Subcontinent and Vicinity
Aponogeton crispus: Sri Lanka.
Aponogeton rigidifolius: Sri Lanka.
Aponogeton undulatus: India and Indochina.
Ceratophyllum demersum (hornwort): worldwide
Ceratopteris thalictroides (oriental water fern): tropics, worldwide
Cryptocoryne wendtii: Sri Lanka
Cryptocoryne willisii: Sri Lanka
Hygrophila corymbosa: India, Malaysia, Indonesia
Hygrophila difformis (water wisteria): India, western Indochina
Hygrophila polysperma: India
Limnophila aquatica: India, Sri Lanka
Rotala macrandra (Tooth-cup): India
Riccia fluitans (crystalwort): worldwide
Vallisneria spiralis (corkscrew Vallisneria): tropics and subtropics
Vesicularia dubyana (java moss): India, Malaya, Java

Southeast Asia
Barclaya longifolia: Burma, Thailand, Vietnam
Ceratophyllum demersum (hornwort): worldwide
Ceratopteris thalictroides (oriental water fern): tropics, worldwide
Cryptocoryne affinis: Malay peninsula
Cryptocoryne cordata: Malay peninsula
Cryptocoryne pontederiifolia: Sumatra, Borneo
Hygrophila corymbosa: India, Malaysia, Indonesia
Hygrophila difformis (water wisteria): India, western Indochina
Limnophila sessiflora: tropical Southeast Asia
Microsorium pteropus (java fern): tropical Southeast Asia
Nymphaea lotus(Egyptian waterlily): East Africa, Madagascar, Southeast Asia
Riccia fluitans (crystalwort): worldwide
Rotala rotundifolia (Tooth-cup): mainland Southeast Asia
Vallisneria spiralis (corkscrew Vallisneria): tropics and subtropics
Vesicularia dubyana (java moss): India, Malaya, Java
Ceratophyllum demersum (hornwort): worldwide

South and Central America
Alternanthera reineckii (copperleaf): tropical America
Cabomba aquatica (fanwort): Northern South America to southern North America
Cabomba caroliniana ( Carolina fanwort): South America to southern North America
Cabomba piauhyensis: Central and South America.
Ceratophyllum demersum (hornwort): worldwide
Ceratopteris thalictroides (oriental water fern): tropics, worldwide
Echinodorus amazonicus ( Amazon sword plant): Brazil.
Echinodorus bleheri: tropical South America
Echinodorus horemanni: southern Brazil.
Echinodorus osiris: southern Brazil
Egeria densa (Brazilian waterweed): Argentina, Paraguay and Brazil
Hemianthus micranthemoides: Cuba, southeastern USA
Heteranthera zosterifolia (Mud plantain): eastern South America
Hydrocotyle leucocephala (water pennywort): Brazil
Ludwigia repens (water primrose): tropical North America and Central America
Myriophyllum aquaticum (water milfoil, Parrot’s Feather): South America, naturalized in Southern North America
Riccia fluitans (crystalwort): worldwide
Sagittaria subulata: American east coast, parts of South America
Samolus parviflorus (water pimpernel): North and South America, West Indies
Vallisneria spiralis (corkscrew Vallisneria): tropics and subtropics

North America

Bacopa caroliniana (water hyssop): southern, central USA.
Cabomba aquatica (fanwort): Northern South America to southern North America
Cabomba caroliniana ( Carolina fanwort): South America to southern North America
Ceratophyllum demersum (hornwort): worldwide
Ceratopteris thalictroides (oriental water fern): tropics, worldwide
Didiplis diandra (water purslane): North America
Echinodorus cordifolius: central and southern North America, Mexico
Hemianthus micranthemoides: Cuba, southeastern USA
Ludwigia repens (water primrose): tropical North America and Central America
Myriophyllum aquaticum (water milfoil, Parrot’s Feather): South America, naturalized in southern North America (not native there)
Nymphoides aquatica (banana plant): Florida.
Riccia fluitans (crystalwort): worldwide
Sagittaria subulata: American east coast, parts of South America
Samolus parviflorus (water pimpernel): North and South America, West Indies
Shinnersia rivularis: Northern Mexico

References:

Scheurmann, Ines. Aquarium Plants Manual. Barron’s