This is a list of commonly available fish that I believe aquarists should think twice before purchasing. Or, if you bought them and didn't know much about them, you should think twice to make sure you can provide the proper home they need to thrive. They all have some sort of special needs that are not always addressed by sellers. I am in no way saying that people should not own these, I am merely pointing out a few of their special needs in case people did not know.
Keep in mind that the fish most commonly available in petstores are very young. The needs I am addressing may not show themselves right away when they fish still a juvenile. Fish grow into their adult behaviors. Just because your fish does not act like this now does not mean it won't in the future.
Also, the old advice that fish grow to fit their tanks is outdated. Scientists have learned a lot more about growth stunting and its effects. Small tanks stunt fish growth which is a painful and unhealthy process. Suggesting a fish will just grow to fit its tank and be fine is very poor advice.
I think all of these can make wonderful additions to the home aquarium as long as people understand their special needs. All the info is presented to the best of my knowledge, research, and experience, and opinions
Think Twice Fish
1. Chinese Algae Eater
They reach over 6 inches, some sources say up to 10 inches, so they need a decently sized tank. As they get older, they quit eating algae and instead prefer to scavenge flakes. They also are known to attach themselves to other fish and suck the slime coat coat off, effectively giving the the fish a hickey which can be very bad for tankmates. They get aggressive to other fish in their space as well. They are best suited for a large tank with fast moving tankmates who can avoid the hickeys.
2. Clown Loach
). Stores often sell them as tiny, cute snail eaters, but they can reach a foot long. In addition, they are a heavy bodied fish so they take up a lot of space. They really should be kept in groups of at least 5 or 6 and need a tank of at least 75 gallons (according to loaches.com).
3. Common Pleco
). They reach well over a foot long. A 125 gallon tank is the minimum I would suggest for this species. They have a very heavy bioload and can be territorial. Also, they have been observed sucking the slime coat off of slower moving tankmates like fnacy goldfish. There are many other smaller species of pleco that are better suited to smaller tanks.
4. Dwarf Gourami
). Many people have great luck with these fish. They are small and beautiful. The only reason for caution (IMO
) is because of dwarf gourami disease which is become rather prevalent in this species. Many of the ones available for purchase are not healthy.
5. Red-tailed black shark
). They reach about 6 inches, but should be kept in a tank of 55 gallons minimum. They get aggressive too. They can terrorize a tank, so tankmates hosuld be chosen carefully. Also, they are especially aggressive with members of their own species and with other bottom dwellers.
6. Green Spotted Puffer
). These guys are so cute and are often sold as fw
fish, but they are not. They can be in fw
for awhile they are young, but that is not permanent. Greenspottedpuffer.net suggests putting them in brackish water by the time they reach 1.5 to 2 inches, and for them to be in full marine water by the time they are 4.5 inches. In addition, gsp have constantly growing teeth and need hard food like snails consistenly, or else you will have to trim their teeth manually. They are not good community dwellers, in part because of their changing salinity requirements and in part because they turn nasty to tankmates. They are not schooling fish, so they do not need friends. Small fish like goby tend to become lunch, larger fish tend to be nipped.
(common and fancy). Stores sell feeder goldies, and not everybody realizes that they turn into monster sized fish. Common goldies can reach 1 to 2 feet and produce a massive bioload. Fancy goldies are smaller, but still produce a huge bioload. It is typically recommended that you need 20g for the first fancy goldy and 10 gallons for every one after that. Common goldies are better suited for ponds than aquariums. Goldfish do not have stomachs, so they need to eat more frequently than other fish sicnethey cannot store food. this trait is what leads to their massive bioload.
8. Bala Sharks
). Balas are not sharks. The name is just attached because of their body shape, but they belong to the same family as minnows and carp. They reach over a foot long and need to be in groups of at least 5. I have heard very mixed reviews about their peacefulness, so I will not testify to that, but they get massive!
9. Red-bellied Pacu
(Colossoma macropomun). Another commonly sold species that gets gignatic. They can get to 2 feet and more. Also, they are often sold under the guise of being vegetarian piranhas, but evidence is emerging to the contrary. There are a decent number of stories of them biting and injuring owners and children. Anybody who wants this fish should watch the episode of Rivermonsters called, "The Mutilator."
). Very commonly available, but they do not stay small. Oscarfish.com says that small ones can grow at a rate of up to an inch a month. They further advise that the fast growth rate means this is not a fish to be put into a small aquarium by a person who figures they will have to upgrade later. They grow to over a foot long and can even weight up to 3.5 pounds. They also are opportunistic feeders and will eat anything that fits into their mouths.
11. Black Ghost Knife
). If 20 inches of fish isn't enough to make you think twice, what about the fact the bgk tend to be aggressive toward fish of a similar size or smaller than them? They do well with larger, peaceful fish, but it takes an enormous aquarium house multiple fish of that size.
I think all of these species are beautiful, but they are often sold under the pretense that they will behave differently than they do. They each have their own special needs that should be considered before adding them, or keeping them, in your aquarium. Think twice to make sure you can give them the proper home so they ca
thrive. If you can, then please put up pictures because these fish are amazing.