Owning fish and designing an aquarium can be great amounts of fun, and as their experience level grows, many aquarists begin to explore the possibility of owning larger or more difficult fish. After all, why stick with a ten gallon freshwater aquarium when you feel confident enough to have a 300 gallon marine aquarium complete with a coral reef? There are some fish, however, that are not suited for home-care and sadly they are all marine animals. While there are a few fresh water fish that are not suitable for the home tank, they can often be placed in a backyard pond when they outgrow their indoor home. These saltwater creatures, however, are simply not meant to be owned or cared for inside a regular aquarium.

Sharks –
While some species of shark may stay small enough to be held in a 300+ gallon tank, the vast majority will outgrow your in-home waters and need to be re-homed in the ocean, something that can be destructive not only for them but for whatever ecosystem they are released into. In addition, sharks are a wild, carnivorous animal. Their nutritional and dietary needs are also difficult to meet as you’re likely to lose your entire community if you keep a shark. As much fun as it seems like it would be, a saltwater shark is just not the right thing for an in-home aquarium.

Squid –
Owning squid is not something that may cross the mind of most people, but those interested in keeping squid should consider octopus instead. Squid require a large, cylindrical tank. Even if you managed to acquire one suitable for the squid, it also cannot be transparent, so you wouldn’t be able to see the squid you owned. When considering their dietary needs in addition to the special tank requirements, it is easy to see why squid are not considered suitable for a home aquarium.

Swordfish –
Though fishing up a swordfish on a fishing trip may be fun and exciting, resist the urge to bring that under-sized specimen home and try to raise it in a tank in your house. This is a fish that will grow to be more than nine feet in length. The largest on record is 14.9 ft and 1400 lbs.! They are carnivorous and their diet requires large quantities of fish meat. This is definitely a fish to throw back, not to bring home!

Manta and Bat Rays –
Their gentle nature and unique physiology may make them desired for the home aquarium, but home aquarists will need to limit themselves to the smaller ray varieties if they want rays in their aquariums. Manta and Bat rays can grow to be up to 10 feet across, weigh more than 200 pounds, and have large appetites with specific dietary requirements. Large rays are definitely best kept in the hands of the professionals.

Cuttlefish/ Nautilus –
Also members of the cephalopod family, the Cuttlefish and Nautilus are not suitable for home aquarium. Poor travelers, the Cuttlefish is unlikely to survive the transport to your home and the most common Cuttlefish, the Common European Cuttlefish, grows to be 18 inches in length and requires a tank of about six feet to be kept well. Nautilus require a deep tank with a temperature below 60˚F. These are deep water dwelling creatures that prefer cool, dark waters and only come out at night. They are not suitable for the home aquarium.