How to Keep a Crustacean in a Community Tank: the Atyid Shrimp

by Robert W. Bly, founder, AquariumDetective.com

A common desire of fish tank owners is to keep a crayfish, crab, or lobster in the tank with their fish.

Ironically, the fish stores stock these fascinating crustaceans for their novelty appeal. Yet when you ask about getting one, they (to their credit) answer honesty in the negative.

The problem is that crayfish, crabs, and lobsters have claws, making them a danger to the fish in the tank. They can use their claws to snag fish that swim too close and make a meal of them.

The Atyid, a family of freshwater shrimp, are the perfect pet for the hobbyist who wants a crustacean in the tank without endangering the fish.

For reasons not fully understood by biologists, the large claws on the front legs of the Atyid have evolved into fan-like appendages. The shrimp constantly fans the water with his two front legs, filtering the water and removing small particles of food for its meal.

I saw one of these filter-feeding shrimp in the fish store a couple of months ago. After being assured it was a safe alternative to the crayfish my kids wanted, we bought the Atyid and added it to the tank.

I am glad we did. To begin with, the promise of nonviolence was 100% accurate. The front fans look incapable of harming a fish. And our freshwater shrimp has shown absolutely no aggression, making no move toward any of the fish.

We occasionally see the shrimp strolling peacefully across the bottom of the tank. Mostly, he remains in a fixed position, waving his from legs in front of him so the delicate fans can filter food particles from the water.

One article I found on the web says, "Even though they are filter feeders by nature, Atyids will use their fans like fingers to lift larger pieces of food from their substrate to their capable mouth."

I have not seen this behavior, but then, we don't feed sinking pellets to our community fish in this tank. I will drop a few in near one of the shrimp's hangouts and see if he takes it.

Our freshwater shrimp prefers to reside in enclosed spaces. We have a flat rock leaning against one wall of the tank. It forms a lean-to that is his second-favorite resting place.

His main hang-out is a decorative cave we bought for the tank. He positions himself standing almost upright in the doorway, giving us a clear view of his feeding process, as his feather-duster front claws fan water toward his mouth, which is constantly moving as he feeds on small bits of food in the water. But even though he likes the cave, he is not aggressively territorial about it.

Some mornings I turn on the tank light and see the Atyid lazing about inside the cave. Other days he is absent, and the cave is either empty or occupied by a gourami or our rainbow eel – though the eel seems to prefer dwelling mostly under the gravel.

Many saltwater and freshwater shrimp are tiny, thin, fragile creatures that look like a perfect snack for larger, more aggressive fish. In this regard, our Atyid, with greater size and bulk, is much safer.

He has a plated exoskeleton similar to a crayfish, giving him ample protection against our tank full of small community fish. I don't know how safe he'd be in a tank of large aggressive cichlids. In any case, our fish ignore him, and never peck at or try to eat him.

He is a solid-looking fellow with a meaty rather than stick-thin body. Depending on the genera (I am not sure which he belongs to), the Atyids can grow to 3 inches or longer. Mine is already closing in on 2 inches.