Sea Turtles....

There are other options if you want a turtle.

Diamondback terrapins live in brackishwater marshes and can found fairly readily in shops that specialize in reptiles. They are pretty cool guys, and don't get too large. You could incorporate one of those guys if you are willing to work within the salinity tolerances of the fish species you plan to use. If you want a true marine tank you aren't going to have any luck with a marine turtle. As everyone has pointed out, they are nearly all on the ESL.
Terrapin.jpg
 
Sea Turtles are incredibly wonderful creatures. Being in South Florida, I got to work with the Sea Turtle Rescue Society. You walk out on the beach here around midnight in certain seasons and watch the "Mom" turtles come up on the beach, dig a hole and lay their eggs. Watching the eggs hatch is the neatest experience. The babies are the cutest little things that don't stay little. I've seen sea turtles that weigh hundreds of pounds. There is no species that is small enough to live in a home aquarium. (unless your Donald Trump and you have a 5,000 gallon aquarium in your home!)

Even if it weren't absoloutely against the law, it would still be a crime to keep something that gets that big and that should have a whole ocean to live in, in a home aquarium.

Come to Florida and go SCUBA diving on our reefs! You'll get to see lots of sea turtles up-close and personal! The ocean is our very own, larger than life, awe inspiring 'reef tank'.

BTW, that Terrapin in the pic is gorgeous!
 
Diamondback Terrapins are not really in the same category as sea turtles. their life styles, body morphology, and requirements are essentially the same as pond turtles, like painted turtles or sliders. They do not have flippers like sea turtles, and are not adapted to permanent and continous life in the water. Sea turtle males never leave the water, and females only leave for a few hours each year to lay eggs. They have a difficult time on land. They are totally adapted to life in the ocean. They can and do travel thousands of miles in the open sea. They are tied to land only by the requirement that their eggs incubate on land. Sea turtles are unlike anything else in the turtle world. They don't really swim, they fly through the water like a bird in the air. They are incredibly fast and agile, wonderful to behold.

Terrapins have legs like ordinary freshwater turtles, not flippers, they do not swim nearly as well, and require dry land resting and basking areas, places where they can dry out and get some direct sun. They cannot be kept in a fish tank unless this dry land area is provided. Small specimens will quickly drown without shallow water and a secure landing area. Terrapins are really just freshwater turtles that have adapted to life in brackish water. They are found in bays, canals, and similar protected water near to land. They can't live in the open sea, and they don't belong in an aquarium either. In general, turtles do not mix well with other creatures in captivity.
 
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