Bettas are probably the fish most commonly kept in small unheated and unfiltered bowls or tanks. At first sight, they seem the ideal fish for this situation. Bettas stay small, growing to approximately 3 inches in length. The waters from which they come are naturally slow-moving or still, and shallow. Bettas have the ability to take in oxygen from the air, which increases their resistance to low oxygen conditions. They dislike fast filtration. They are solitary in temperament and swim slowly. All these things makes them seem an ideal candidate for the small unfiltered bowl.

Problems With Betta Bowls

However, the waters from which they come are warm: the average temperature is 24-30C (75-86F), according to Fishbase.org. This is much higher than the temperature in most people’s houses, especially in the winter. While they will survive in an unheated bowl provided the room is decently warm, housing them like this seems questionable. When kept at lower temperatures, Bettas are less active and are more susceptible to disease.

While Bettas do much better than most fish in low-oxygen conditions, they still suffer from build up of fish wastes when kept in small bowls. Such bowls must be cleaned much more frequently than a tank to prevent build-up: 100% water changes multiple times per week. The long fins of male bettas are susceptible to finrot, and dirty water increases the likelihood of problems.

Some of the objects in which Bettas are kept are too small for any fish. In petstores, they are often kept in hand-size bowls, or worse, in plastic drinking cups. I’ve even seen a few in containers narrower than their body was long, not counting the fins. Moral sentiment and the fish’s health aside, this is not a sensible way to sell these fish, as they cannot display properly and their beauty is completely invisible.

Advantages of a Heated Aquarium

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-lighted aquarium is a truly stunning sight.

Sources:

Fishbase.org

RandomWiktor. Tiny Mud Puddles and Other Lies: Myths and Misconceptions About Our Beloved Bettas

The Walking Catfish, Clarias batrachus, is a very large catfish sometimes seen in the aquarium trade. It is also used as a food fish. It is native to Southeastern Asia, but it has been introduced to numerous other places where it has become an invasive and predatory pest. Once in an area, it is hard to contain because it can walk across land, entering aquaculture ponds and eating the fish, or entering seasonal wetlands not normally inhabited by fish to eat tadpoles.

It has been introduced to Indonesia (Sulawesi), the USA, Hong Kong, Taiwan, China, UK, Papua New Guinea, Guam, Taiwan, Thailand, and possibly the Philippines. This species has been nominated as one of the world’s top 100 invasive species. The method of invasion involves escapees from the pet trade as well as aquaculture. It is illegal to keep this fish in some countries, as well as in many US states.

Very cold water kills Walking Catfish, so if your area goes below freezing in the winter this fish should not become invasive even if some manage to escape. In many areas with warmer water it is often illegal to keep them without a permit. Even if they are legal in a warmer area, it is still very important not to let them escape from their tank.  Because of their ability to walk on land, the possibility of escape is much greater than with most tropical fish.  Make sure their aquarium has a strong and tightly fitting lid so that they cannot push it up and wander off.

Sources:

Global invasive species database. Compiled by Invasive Species Specialist Group (ISSG)

Brogan, Christine. 2003 Introduced Species Summary Project

Pond snails are the snails that turn up unintentionally when you buy aquatic plants. They breed prolifically and are often considered a pest. However, these snails have their good points: they are easy to feed, help keep the tank free of uneaten fish food, eat algae, stay small, do well at both tropical and low temperatures and are not aggressive towards other animals. They are safe inhabitants for a shrimp tank, which is especially valuable when you consider that the majority of fish cannot be kept with shrimp without the shrimp becoming dinner.

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

It all depends on species…

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

The Corydoras Catfish

Catfish leaps upward
Hovering in mid-water
Hoping for some food.

The Betta

The betta dances
Before the glass’s mirror
Rival dances back.

The Neon Tetra

Swimming together
To confuse bigger fishes
They sparkle with light.

The Guppy

Tail streaming behind
The small fish wiggles onward
Looking for a mate.

The Goldfish

Slow and yet graceful
They sail on through the water
Each alone yet not.

Note: Next week’s post will be a proper article.

Everyone who keeps tropical fish for longer than a few months makes mistakes early on that they wish they could tell their younger selves to avoid. I was six years old when I started keeping fish, and I made a lot of mistakes. In the hope that you will be able to avoid some of them, I present 10 of my worst mistakes here:

One: Not do research. When I was first starting out, most of my problems stemmed from this.

Two: Not do regular partial water changes. Because I hadn’t done number one, I didn’t realize that I was supposed to do this, or how one should do this.

Three: Put too many fish in the aquarium. This compounded problem two.

Four: Assume fish are short lived. A few fish, like annual killifishes, live only a few months in nature but a Corydoras catfish can live for up to seven years in captivity and a goldfish can reach 20 years of age. If you make this wrong assumption, you may not notice you are doing something wrong.

Five: Buy one of each species. Many fishes are schooling and do not do as well without the company of their own kind.

Six: Keep goldfish in a goldfish bowl. Common goldfish can grow up to 12 inches in length and produce large amounts of waste. They do not belong in goldfish bowls.

Seven: Started with too small a fish tank. A five gallon tank makes a perfectly good aquarium, but water parameters can change quickly and you can’t keep many fish in there.

Eight: Not feed bottom feeders sinking food and depend on one brand of flake food for everything. Corydoras catfish get hungry and don’t feed off the surface. Fish benefit from a varied diet just as we do.

Nine: Keeping a Betta in a community tank without a plan B or enough hiding places for fish to get away. It killed one of my Neon Tetras, so we put the Betta in a breeding trap that wasn’t really big enough for it.

Ten: Put a Pygmy Gourami in with Cherry Shrimp. Pygmy Gouramis may have small mouths, but they regard shrimp as food and that one fish harassed the shrimp unmercifully. If it hadn’t been for the extremely thick live plants I think I would probably have lost all my Cherry Shrimp.

The last one wasn’t all that long ago, so such mistakes aren’t limited to beginners. No matter how much you think you know, do your research! And if you possibly can, keep a spare tank for quarentine, hospital use and unexpected animosities.

While most people thinking of invertebrates for the aquarium are thinking of marine invertebrates, there are a surprising number of freshwater invertebrates that make excellent tank inhabitants.  Many freshwater invertebrates do not require large amounts of space, making them ideal for Nano tanks or even goldfish bowls.  Some eat algae or uneaten fish food, while others are stunningly beautiful.  Sometimes such useful attributes even belong to the same creature.  However, freshwater invertebrates don’t always have the same requirements as fish and the requirements differ considerably between different species.

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.

Certain fishes are often kept in bowls or small plastic aquariums that lack heating and filtration equipment.   The fish most often kept in this way include goldfish, bettas, white cloud mountain minnows, and danios.  Each of these fishes have different pros and cons when it comes to keeping them in this fashion.

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.

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 help you avoid buying fishes that will outgrow your tank.
Oscars: Astronotus ocellatus
Tinfoil Barb: Puntius schwananfeldi
Bala Shark: Balantiocheilus melanopterus
Apollo Shark: Luciosoma spilopleura
Six-barred Distichodus: Distichodus sexfasciatus (may grow larger in wild)
Banded Leporinus: Leporinus fasciatus
Red Piranha: Natterer’s Piranha: Rooseveltiella nattereri
Clown Loach: Botia macracantha (may grow larger in nature)
Green Snakehead: Channa gachua, Ophiocephalus kelaartii (often only 8 in)
Four-eyed Fish: Anableps anableps
Cuckoo catfish (female): Synodontis multipunctatus
Royal Panaque, Royal plecostomus: Panaque nigrolineatus (16 in)
Gold Nugget Plecostamus: Scobinancistrus sp.
Giant Whiptail, Golden Whiptail: Sturisoma aureum

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

Corydoras are among the best tropical fish for the home aquarium. They are small, they aren’t aggressive toward smaller fish, they are hard for bigger fishes to eat, and they help keep the tank clean by scavenging food off the bottom.  Despite rumors to the contrary, they do not eat fish poop and they do require feeding.  They prefer to eat food off the bottom so they need to be fed food that sinks.

They will happily eat sinking tablet foods. There are several different types of these which can be found at most pet stores. They also enjoy frozen foods, especially frozen blood worms. Live worm-type foods are eagerly accepted so long as they are small enough for the fish to eat.

Types of Corydoras

There is an astonishing number of Corydoras species. The number of named Corydoras species was 156 in 2006 (Fuller, 2006), with new species being discovered faster than they could be named. These fish originally come from South America, mainly from the great river basins of the Amazon, the Orinoco and the Rio Negro.

The most common Corydoras species in the tropical fish hobby is the Bronze Corydoras, Corydoras aeneus, followed by the Peppered Corydoras, Corydoras paleatus, but there are many are other species available. They range in size from scarcely over an inch in the case of Corydoras hastatus, pygmaeus, and habrosus to approximately 3 inches for Corydoras aeneus and others. Fish that look like Corydoras but are larger are probably in one of the genera Brochis or Schleromystax, both of which are closely related to the genus Corydoras. The common Corydoras are usually between two and three inches in size with Corydoras aeneus being approximately three inches when adult.

With so many species, there are many different color patterns available. Most Corydoras patterns contain contrast in dark and light coloring, or large amounts of gray. Different color patterns will appeal to different people, but the intricate pattern of spots on Corydoras trilineatus makes it one of the most beautiful species.

Corydoras Behaviour

Corydoras school. Almost all species are bottom dwellers and enjoy digging in the gravel. The schools often sit on the bottom or hover and swim just above it. The exceptions are the dwarf species which will often be found schooling in mid-water as well as near the bottom. These smallest corydoras have a slightly different and more streamlined shape when compared to the Bronze Corydoras. The shape of these small Corydoras is probably due to their preference for mid-water swimming where a more streamlined shape is useful.

Corydoras can absorb oxygen from air taken into the gut and for this reason will sometimes dart to the surface for a breath of air and then back down to the bottom. This is normal behavior, but if all your Corydoras are doing this constantly then there may be inadequate dissolved oxygen in your tank.

I have kept Corydoras for many years and I have never seen recognisable aggressive behavior by Corydoras against members of their own species or any other, including towards much smaller individuals that have beaten them to the food, and partially grown fry of other fish species.

Corydoras are egg-depositors and will lay eggs on any available flat surface including the walls of the tank, the tank heater, and tank decorations. Reports on whether they eat their eggs are mixed so you may wish to separate the eggs from the adults.

With their even temperament, myriad species, and comical appearance, Corydoras are much more than just tank scavengers. When given what they need to flourish they are a fascinating and beautiful addition to the tank.

References:

Fuller, I. 2006 Starting with Corydoras. http://www.scotcat.com/articles/article33.htm