Most aquarium beginners are most of the time stranded on which fish to start with. They could be in a fish store looking at a little sucker mouth catfish unaware of what they can grow to. In actuality, they can grow as long as 1 foot and beyond and can also live for more than 20 years. Are you aware that the little cute white (and black) and orange oscars often get very large and drops quite a heavy amount of waste in the tank? It is quite sad that most beginners are unaware of this fact.

So, which fish should you avoid?

Discussed below is a list of 11 species that are very popular to an extent that the world’s biggest retail stores sell them in the pet section. To save you the hassle, you should consider not having this fish until you someday get the real urge to keep fish as well as maintain the tank properly. Setting up specialized tanks for specific species can be done at later stages of the hobby. They are simply not so good for a starter fish keeper. They demand quite a lot from the hobbyist and often demanded a bit more than what is offered in the community tank. Specialized filtration or water qualities is just one of these demands they make. They are also are generally aggressive; claiming part or all of the aquarium.

Pacu (colossoma Spp)

Pacu (colossoma Spp) freshwater fish beginning fishkeepers should avoid - Aquaticmag (17)  11 feshwater fish beginning fishkeepers should avoid Pacu colossoma Spp freshwater fish beginning fishkeepers should avoid Aquaticmag 17

The pacu have at many times been sold as a vegetarian. They are considered to be cousins to topiranha, since they both come from the same Characidae family. One major character trait attributed to pacu is its size after reaching maturity. Most of the unknowing beginners are misled by this trait. Most pacu that are seen in the pet store often have an awesome coloration and could be just 2 to 3 inches in length. However, within their first year, they will have outgrown a 55 gallons tank and will still continue growing as well as will even exceed a weight of 10 pounds. Most confusing of all is that their colors fade. At all cost, avoid this fish, not unless you have a very good and well sized outdoor pond. Also consider avoiding any of the local fish stores that sell you any fish without telling you further details of how big they can get.

Red tailed shark (Epalzeorhynchos bicolor)

Red tailed shark (Epalzeorhynchos bicolor) freshwater fish beginning fishkeepers should avoid - Aquaticmag  11 feshwater fish beginning fishkeepers should avoid Red tailed shark Epalzeorhynchos bicolor freshwater fish beginning fishkeepers should avoid Aquaticmag

This type of fish is largely popular in the hobby due to its astonishing coloration and a body that resembles that of a shark. It’s highly territorial nature discredits it from being a favorite. However, it isn’t that difficult to keep this fish. It does like being alone, and is unaccommodating for other red tailed sharks or other similar species like the rainbow shark. I have witnessed them harass other smaller fish in my community tank. This is however the way most starters develop their very fist tanks. If you consider keeping the red tailed shark, you will then have to ensure that your tank is less populated with shy fish as they may be tortured by this shark.

Plecostomus

Plecostomus freshwater fish beginning fishkeepers should avoid - Aquaticmag  11 feshwater fish beginning fishkeepers should avoid Plecostomus freshwater fish beginning fishkeepers should avoid Aquaticmag

Do you have any algae hitch in your tank? If you answer yes, then you need to have plecostomus. This is usually the remedy to most folks’ algae challenges, instead of finding out what is the genesis of the algae. Plecostomus is a very well-known fish such that even the world’s largest discount retailer stocks them. The most important thing to note here is that they are usually just very few specimens that are 3 to 4 inches long. This is however very misleading. You should beware of this particular fish such as the Bristlenose Pleco. As it grows, it gets longer and will soon be very big. Most starters often set off with 20 to 30 gallons fish tanks. If you consider adding in a plecostomus in your tank, it will be like introducing a killer whale to a swimming pool. This fish can grow quite lengthy, actually 12 inches and above. I have come across a big specimen (previous pets were set free) schooling in Manoa creek on O’ahu, (feasting on algae). Just to clear the air, they are massive pollutants, meaning that they defecate quite a lot.

Oscar (Astronotus Ocellatus)

Oscar (Astronotus Ocellatus) freshwater fish beginning fishkeepers should avoid - Aquaticmag  11 feshwater fish beginning fishkeepers should avoid Oscar Astronotus Ocellatus freshwater fish beginning fishkeepers should avoid Aquaticmag

The Oscar Fish is another species that is readily available in the world’s largest discount fish retailers and can be bought at all the local pet stores as well as the big box pet stores. They are available as fingerlings in their albino colors and normal black and white colors. Tanks of 50 gallons or more are good for these fish. The 80 to 100 gallon tanks are much better instead of a typical size for the beginner tank. Oscar, which is a member of the cichlid family eat almost every other fish that can fit in its mouth. It is for this reason that some hobbyist feed them with feeder fish as well as the famous gold fish, regardless of this practice being unnecessary. For the starters, this fish may be quite demanding and tasking. Its large size puts it in them in the “should avoid section”.

African cichlid

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According to me, African cichlids of the Rift Lakes are the most attractive freshwater fish any hobbyist can keep. However, they are quite aggressive like the cockatoo cichlid or convict cichlid. Most starters may not put up with this practice where other occupants of the tank are torn into pieces by the cichlid. Despite killing other types of fish in the community tank, they often go to an extent of fighting amongst themselves. Regardless of their beauty, it is wise for the starters to leave these fish to the more advanced hobbyist following their territorial nature, specialized attention and the weekly routines for changing water in their tanks.

Silver Arowana (Osteoglossum bicirrhosum)

Silver Arowana (Osteoglossum bicirrhosum) freshwater fish beginning fishkeepers should avoid - Aquaticmag  11 feshwater fish beginning fishkeepers should avoid Silver Arowana Osteoglossum bicirrhosum freshwater fish beginning fishkeepers should avoid Aquaticmag

To most of the less conscious beginners who are very unaware of the size to which the silver arowana can grow to, they are often sold to them as baby arowanas. Alongside the Oscar and other tank busting fish, this fish too has a behavior of eating anything that fits its mouth. It needs quite a large and lengthy aquarium with the ideal average being three times the length. The Silver Arowana can grow to a length of 3 feet. They are usually very beautiful in their very tender age but then, they later grow to be so big with high urge for food and produce massive wastes.

Bala Shark (Balantiocheilus melanopterus)

Bala Shark (Balantiocheilus melanopterus) freshwater fish beginning fishkeepers should avoid - Aquaticmag  11 feshwater fish beginning fishkeepers should avoid Bala Shark Balantiocheilus melanopterus freshwater fish beginning fishkeepers should avoid Aquaticmag

The Bala shark resembles the shark and is closely related to the carps and the true minnows. It is in the Cryprinidae family. This fish can grow to a length of 12 inches or more. This remains to be quite huge for the starters and their medium community tanks. This fish is very wonderful especially in the groups of six or more.

Discus (Symphysodon aequifasciatus)

Discus (Symphysodon aequifasciatus, S. heckel and S. haraldi) freshwater fish beginning fishkeepers should avoid - Aquaticmag  11 feshwater fish beginning fishkeepers should avoid Discus Symphysodon aequifasciatus S

Alongside the African cichlids, this fish is also top ranking in the beauty arenas. They do well both in fresh and salty water. It is also a very peaceful fish with a calm behavior. It requires water with specific parameters as well as very close attention, including quite a large and a tall tank with many live floating and rooted plants. A routine water changing practice must be followed. Due to these factors, discus will be a big bother to any starter. This fish should be left to those hobbyists who are advanced.

Glass Catfish (Kryptopterus bicirrhis)

Glass Catfish (Kryptopterus bicirrhis) freshwater fish beginning fishkeepers should avoid - Aquaticmag  11 feshwater fish beginning fishkeepers should avoid Glass Catfish Kryptopterus bicirrhis freshwater fish beginning fishkeepers should avoid Aquaticmag

Have you ever seen a living creature having a transparent body where you don’t struggle to see through? Well, this is one major feature that makes glass catfish quite interesting to keep looking at. Despite being available at the pet store and the big box pet store, most of them are caught in their very natural habitats. They are however very prone to bacterial infections. It being a shoaling fish, it is wise to keep them into groups of not less than six fish. If they are less than six, they become very vulnerable and can die in the tank.

Otocinclus (Otocinclus sp.)

Otocinclus (Otocinclus sp.) freshwater fish beginning fishkeepers should avoid - Aquaticmag  11 feshwater fish beginning fishkeepers should avoid Otocinclus Otocinclus sp

these are a subtle sucker mouth catfish species that needs absolutely clean and well circulated water to resemble their natural habitat. The Otocinclus are caught from its natural habitat. For this reason, they are stressful to keep than the captive bred fish, though, with the right water parameters and the right diet, they can be kept with much success. These fish require the tanks that are very densely planted with live plants, rocks and some fine substrate. The reason for this is that they are herbivorous. They love eating algae but also need a supplement of live plants like peas, lettuce and zucchini. You can also consider adding the algae tablets that most hobbyists keeping this fish use. To successfully keep this fish requires proper monitoring of the water as well as providing the best supplements with the vegetable matter.

Koi (Cyprinus carpio)

These types of fish have been seen in all sorts of water gardens while others are spotted at the backyard ponds. This is basically because they flourish in this kind of habitat; not in the fish tank. They are very beautiful and can grow to a length of 2 feet and weigh several pounds. In a bizarre scenario, they require much more water than most tanks can offer. Essentially, they need 100 to 200 gallons of water per every adult fish. This is way too far than most beginners can go. Having been seen available in the local fish retailers’ stores in a water tank, it should never be mistaken that they will be kept in a tank when taken home. You will be surprised if you try this.

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I'm not the greatest writer in the world but I like to educate people on how to setup and maintain a beautiful shrimp tank that friends and family will be envious about. It's a great hobby and takes a bit of knowledge but once you get it down - it seriously beats looking at a screensaver of fishes!