When it comes to keeping an aquarium, there are just some types of fish that shouldn’t be kept as pets – especially by the novice aquarist. The reasons vary, but in most cases, the fish either get too large for the average home aquarium, or they require very specialized care. Here are a few of the top fish that really don’t belong as a pet in an aquarium.

1. Freshwater pufferfish.

Although freshwater puffers are really cute, they don’t make good aquarium pets if they are going to be kept in a community fish tank – they truly are a specialist fish. In general, freshwater puffers However, if you’re willing to feed them the appropriate diet (i.e. not feeder goldfish), and give them a tank of their own, then they can provide you with many years of enjoyment.

2. Common goldfish.

The common goldfish is often placed in a fish bowl, which is truly a barbaric practice – a bowl just can’t stay clean, no matter how often you change the water, and it cannot support a healthy biological filter. The common goldie can get larger than a foot, and they should be left to outdoor ponds or appropriately sized tanks.

3. Common plecos.

Most people get a pleco to help clean up the algae in their fish tank. However, depending on the species, this is a very bad idea. For instance, some plecos aren’t solely herbivorous fish, and in some instances, like the common pleco, they can reach lengths of 2 ft and larger.

4. Pacu fish.

The pacu gets huge – like throw it in a frying pan and serve your family for dinner huge. Some specimens have been known to exceed 3 ft. In addition to their large size, pacu fish are also schooling, which means they not only require a small pool for a tank, but they also need at least 6 other fish for company.

5. Red tailed catfish.

RTC’s are very beautiful fish from the Amazon, however, they really have no place in the home aquarium – they get the size of a small child, and there is no way to prevent them from growing into giants.

6. Green spotted puffer.

This is a very common fish in many pet stores, and unfortunately, it’s almost always labeled as a freshwater puffer. However, they are not a freshwater fish – green spotted puffers are brackish water puffers. This means that they require marine salt in their water – not just aquarium salt.

There are of course exceptions to the rule – some people really can provide for the above fish, and a few do make great pets if all of their basic needs are met. However, none of them make a good impulse purchase because you will definitely get more that you bargained for.