nmonks
A stroke of the brush does not guarantee art from
Steelhealr has written a great topic on fish to avoid, certainly by inexperienced aquarists. It's a surprise to many aquarists new to the hobby that a lot of the stock for sale in shops is either not suitable for home aquaria, or requires water conditions other than those in the average tank.
This article is a follow-up of sorts, with fishes that regularly cause problems of one sort or another. None are "bad fish", but the idea of putting them here is so that beginners might have some idea of fishes that aren't zero maintenance, and so avoid them if they want.
Cheers,
Neale
-----------------------------------
Dwarf Gourami
In most ways these are ideal community fish: colourful, peaceful, and small. However, most of the commercially available stock is infected with mysterious bacterial infections that seem very difficult to cure. On the farms where they are bred, use of antibiotics prevents any problems, but once they are sent to the retailer, the bacteria multiply. Avoid buying fish from any tank that has even one sickly looking fish. The signs of the disease include white or bloody patches on the skin, lethargy, and heavy breathing. Eventually, the fish dies.
The disease can be passed to (or caught from) other gouramis, but most other gouramis don'd die from the disease. If you want a gourami, consider one of the other species. Lace and moonlight gouramis in particular may be larger, but they are much more hardy and long-lived. If you still want to keep dwarf gouramis, quarantine them before adding them to your tank, keeping the dwarf gouramis in their own aquarium for 4 to 8 weeks, and medicate with the antibacterial product of your choice (e.g., Interpet #9).
Neon Tetras
Like dwarf gouramis, neon tetras are bred intensively on fish farms where much use is made of antibiotics instead of clean husbandry. The result is that neons are now among the cheapest aquarium fish for sale, but with the downside that most, perhaps all, are infected with the dreaded Neon Tetra Disease parasite.
Again, this is incurable. Very occasionally, fish recover, but usually sickly fish die within a few days. The symptoms are unmistakeable: the fish goes off-colour, hides away from the school, and eventually cannot swim properly. It is critical to remove the fish at this stage, because the parasite usually jumps from the diseases fish to the healthy ones when the sick fish has died. Because other fish tend to nibble on the corpse, the parasite gets eaten by the healthy fish.
Quarantining neon tetras is an excellent idea, but at the very least, never buy neons from a shop where you can see sickly specimens. Neon tetra disease can infect other species of fish, including things like angelfish and goldfish, but surprisingly enough most other tetras are either resistant or immune to it. Cardinal tetras can catch the disease, but are less sensitive to it, and so make a better choice if you want to minimise this problem. Tetras such as bleeding hearts and diamonds don't seem to get it at all.
Mollies -- all types
Mollies must have hard, alkaline water, and most specimens need water to which 3g/litre salt (or more) is added. Adding salt improves their colour and health, and kept in slightly salty water they are very hardy fish, ideally suited even for maturing aquaria during the cycling period. Kept without salt, they are delicate, and prone to fungus, fin-rot, and the "shimmies", where they cannot swim properly and seem to tread water, wobbling from side to side.
Adding salt is easy (buy marine salt from the aquarium shop, not tonic salt); but not all fish appreciate salty water. As a general rule, catfish, tetras, and barbs don't like salt, but livebearers, cichlids, rainbowfish, and gobies are fine with it. So if you're keeping your mollies with guppies and platies, there's no reason not to add salt, and you'll be doing your fish a big favour.
Pufferfish
Puffers are popular fish, and most species are quite hardy and easy to keep. However, very few of them are community fish, so most need to be kept either with their own species, or as a single specimen in its own tank. Puffers may also need brackish rather than fresh water, and they also have a specialised diet, needing things like snails and unshelled shrimp rather than flake. Puffers are definitely fun fish, but think of them as subjects for your second aquarium rather than as oddballs for the community tank.
Tiger Barbs (a.k.a. moss barbs, albino barbs)
Most barbs are excellent community fish (though some need subtropical water conditions, and a few grow very large). Tiger barbs are an exception. They are confirmed fin-nippers. Kept in large groups (twelve or more) they nip less, but even then, don't keep them with anything other than fast-moving, short-finned tankmates. Tetras, danios, loaches, Corydoras, etc., would be fine, but angelfish, gouramis, and guppies are not suitable tankmates.
If in doubt, opt for the similar five-banded barb. It's similar in shape and colour, and while less outgoing, it is completely peaceful.
Serpae Tetras (a.k.a. jewel tetras, callistus tetras, flame characin)
Serpae tetras, Hypessobrycon callistus, are fin-nippers, and are best kept only with other tetras. While very pretty, and an oustanding addition to a planted aquarium, where their warm colours really show up nicely, these aren't reliable community fish. For an alternative, opt for the bleeding heart tetra, Hyphessobrycon erythrostigma, or the flame tetra, Hypessobrycon flammeus.
Black Widows (a.k.a. petticoat tetra, black skirt tetra)
A widely sold, angelifish-like tetra also available in an albino form as well as long-finned varieties. Another fin-nipper, so mix with fast-moving species without long fins.
Ram Cichlids
Commonly called "rams", these fish are again a species that has been bred in vast quantities without much care for health or quality. Cheap stock has poor colours, inconsistent behaviour, and a short lifespan. They suffer from a variety of problems including hole-in-the-head disease. Sometimes they can recover with the correct treatment, but not always. Quarantining the fish is essential, and never buy from a place where you see sickly rams in with the healthy ones. Ideally, hunt out a retailer with wild fish, locally bred stock, or stock that has been imported from Western Europe (the so-called German rams). These are much hardier. Wild fish will need soft, acid water, but local and German rams are generally more adaptable.
Upside-down Catfish
Upside-down catfish are fin-nibblers at times, so avoid keeping with long-finned fish. They are fine with tetras, barbs, cichlids, etc. Another issue with upside-down catfish is that not all stock offered for sale is "the real thing". Synodontis nigrita is often sold instead. It grows to around 15 cm long and is a fairly aggressive, territorial fish, so not an ideal community fish. Juveniles of that species closely resemble the true upside-down catfish. The best way to tell them apart is that only the true upside-down catfish has small white spots on the back.
Angelfish (thanks to KathyM for reminding me to put angelfish here!)
Angelfish can be good community fish, but they grow relatively large (potentially 10-15 cm long) and are predatory. They will eat neons, glowlights, small guppies, etc. Angelfish are schooling fish when young, but adults form pairs and are more territorial; in aquaria, territorial fish can bully other angelfish in the tank, and sometimes other fishes as well. Conversely, they will be attacked by nippy fish such as tiger barbs, serpae tetras, and black widows, and may be bullied by aggressive species such as blue gouramis and cichlids such as firemouths and convicts.
Angelfish are lovely fish, but work best in a community tank built around them rather than simply added to any random collection of fish. They work well with Corydoras, bristlenose catfish, hatchetfish, and medium-sized, non-aggressive tetras such as diamond tetras and rummy-nose tetras. They can work well with peaceful gouramis and loaches, too.
Be aware also that a lot of the "cheap" angelfish are relatively poor quality. Typically, such fish have ragged, uneven finnage, do not grow as large as they should, and tend to have strange personalities. Almost all make appalling parents, eating their eggs and fry. Some strains in particular, such as the black angels, seem to be more aggressive towards tankmates than the others. Good quality, pedigree angelfish are, unfortunately, expensive, but as with many things in life, you get what you pay for.
Dawn Tetra
See this reply.
Guppies
See this reply.
Oddballs
See this reply. Knifefish, spiny eels, bichirs, freshwater soles, gobies, and other unusual fish can make excellent community tank fish, but they may also have very specific requirements that means they simply won't work in your tank. Read up on Oddball Fish before purchasing them.
This article is a follow-up of sorts, with fishes that regularly cause problems of one sort or another. None are "bad fish", but the idea of putting them here is so that beginners might have some idea of fishes that aren't zero maintenance, and so avoid them if they want.
Cheers,
Neale
-----------------------------------
Dwarf Gourami
In most ways these are ideal community fish: colourful, peaceful, and small. However, most of the commercially available stock is infected with mysterious bacterial infections that seem very difficult to cure. On the farms where they are bred, use of antibiotics prevents any problems, but once they are sent to the retailer, the bacteria multiply. Avoid buying fish from any tank that has even one sickly looking fish. The signs of the disease include white or bloody patches on the skin, lethargy, and heavy breathing. Eventually, the fish dies.
The disease can be passed to (or caught from) other gouramis, but most other gouramis don'd die from the disease. If you want a gourami, consider one of the other species. Lace and moonlight gouramis in particular may be larger, but they are much more hardy and long-lived. If you still want to keep dwarf gouramis, quarantine them before adding them to your tank, keeping the dwarf gouramis in their own aquarium for 4 to 8 weeks, and medicate with the antibacterial product of your choice (e.g., Interpet #9).
Neon Tetras
Like dwarf gouramis, neon tetras are bred intensively on fish farms where much use is made of antibiotics instead of clean husbandry. The result is that neons are now among the cheapest aquarium fish for sale, but with the downside that most, perhaps all, are infected with the dreaded Neon Tetra Disease parasite.
Again, this is incurable. Very occasionally, fish recover, but usually sickly fish die within a few days. The symptoms are unmistakeable: the fish goes off-colour, hides away from the school, and eventually cannot swim properly. It is critical to remove the fish at this stage, because the parasite usually jumps from the diseases fish to the healthy ones when the sick fish has died. Because other fish tend to nibble on the corpse, the parasite gets eaten by the healthy fish.
Quarantining neon tetras is an excellent idea, but at the very least, never buy neons from a shop where you can see sickly specimens. Neon tetra disease can infect other species of fish, including things like angelfish and goldfish, but surprisingly enough most other tetras are either resistant or immune to it. Cardinal tetras can catch the disease, but are less sensitive to it, and so make a better choice if you want to minimise this problem. Tetras such as bleeding hearts and diamonds don't seem to get it at all.
Mollies -- all types
Mollies must have hard, alkaline water, and most specimens need water to which 3g/litre salt (or more) is added. Adding salt improves their colour and health, and kept in slightly salty water they are very hardy fish, ideally suited even for maturing aquaria during the cycling period. Kept without salt, they are delicate, and prone to fungus, fin-rot, and the "shimmies", where they cannot swim properly and seem to tread water, wobbling from side to side.
Adding salt is easy (buy marine salt from the aquarium shop, not tonic salt); but not all fish appreciate salty water. As a general rule, catfish, tetras, and barbs don't like salt, but livebearers, cichlids, rainbowfish, and gobies are fine with it. So if you're keeping your mollies with guppies and platies, there's no reason not to add salt, and you'll be doing your fish a big favour.
Pufferfish
Puffers are popular fish, and most species are quite hardy and easy to keep. However, very few of them are community fish, so most need to be kept either with their own species, or as a single specimen in its own tank. Puffers may also need brackish rather than fresh water, and they also have a specialised diet, needing things like snails and unshelled shrimp rather than flake. Puffers are definitely fun fish, but think of them as subjects for your second aquarium rather than as oddballs for the community tank.
Tiger Barbs (a.k.a. moss barbs, albino barbs)
Most barbs are excellent community fish (though some need subtropical water conditions, and a few grow very large). Tiger barbs are an exception. They are confirmed fin-nippers. Kept in large groups (twelve or more) they nip less, but even then, don't keep them with anything other than fast-moving, short-finned tankmates. Tetras, danios, loaches, Corydoras, etc., would be fine, but angelfish, gouramis, and guppies are not suitable tankmates.
If in doubt, opt for the similar five-banded barb. It's similar in shape and colour, and while less outgoing, it is completely peaceful.
Serpae Tetras (a.k.a. jewel tetras, callistus tetras, flame characin)
Serpae tetras, Hypessobrycon callistus, are fin-nippers, and are best kept only with other tetras. While very pretty, and an oustanding addition to a planted aquarium, where their warm colours really show up nicely, these aren't reliable community fish. For an alternative, opt for the bleeding heart tetra, Hyphessobrycon erythrostigma, or the flame tetra, Hypessobrycon flammeus.
Black Widows (a.k.a. petticoat tetra, black skirt tetra)
A widely sold, angelifish-like tetra also available in an albino form as well as long-finned varieties. Another fin-nipper, so mix with fast-moving species without long fins.
Ram Cichlids
Commonly called "rams", these fish are again a species that has been bred in vast quantities without much care for health or quality. Cheap stock has poor colours, inconsistent behaviour, and a short lifespan. They suffer from a variety of problems including hole-in-the-head disease. Sometimes they can recover with the correct treatment, but not always. Quarantining the fish is essential, and never buy from a place where you see sickly rams in with the healthy ones. Ideally, hunt out a retailer with wild fish, locally bred stock, or stock that has been imported from Western Europe (the so-called German rams). These are much hardier. Wild fish will need soft, acid water, but local and German rams are generally more adaptable.
Upside-down Catfish
Upside-down catfish are fin-nibblers at times, so avoid keeping with long-finned fish. They are fine with tetras, barbs, cichlids, etc. Another issue with upside-down catfish is that not all stock offered for sale is "the real thing". Synodontis nigrita is often sold instead. It grows to around 15 cm long and is a fairly aggressive, territorial fish, so not an ideal community fish. Juveniles of that species closely resemble the true upside-down catfish. The best way to tell them apart is that only the true upside-down catfish has small white spots on the back.
Angelfish (thanks to KathyM for reminding me to put angelfish here!)
Angelfish can be good community fish, but they grow relatively large (potentially 10-15 cm long) and are predatory. They will eat neons, glowlights, small guppies, etc. Angelfish are schooling fish when young, but adults form pairs and are more territorial; in aquaria, territorial fish can bully other angelfish in the tank, and sometimes other fishes as well. Conversely, they will be attacked by nippy fish such as tiger barbs, serpae tetras, and black widows, and may be bullied by aggressive species such as blue gouramis and cichlids such as firemouths and convicts.
Angelfish are lovely fish, but work best in a community tank built around them rather than simply added to any random collection of fish. They work well with Corydoras, bristlenose catfish, hatchetfish, and medium-sized, non-aggressive tetras such as diamond tetras and rummy-nose tetras. They can work well with peaceful gouramis and loaches, too.
Be aware also that a lot of the "cheap" angelfish are relatively poor quality. Typically, such fish have ragged, uneven finnage, do not grow as large as they should, and tend to have strange personalities. Almost all make appalling parents, eating their eggs and fry. Some strains in particular, such as the black angels, seem to be more aggressive towards tankmates than the others. Good quality, pedigree angelfish are, unfortunately, expensive, but as with many things in life, you get what you pay for.
Dawn Tetra
See this reply.
Guppies
See this reply.
Oddballs
See this reply. Knifefish, spiny eels, bichirs, freshwater soles, gobies, and other unusual fish can make excellent community tank fish, but they may also have very specific requirements that means they simply won't work in your tank. Read up on Oddball Fish before purchasing them.
Might be worth adding about the low quality of a lot of angelfish leading to a predisposition to disease? You're the expert though, not me *lol*.
I've never tried them again.
They're not even suitable companions for tiger barbs and small danios.
