Grouper in Roatan gets a teeth cleaning by his little friend

Groupers are intelligent fish, and capable predators. They ambush their prey or actively hunt fish, octopus, and crustaceans. They create a powerful suction as they open their mouths and inhale their prey. Small fish are wise to avoid the powerful jaws of the grouper.
But the ocean is a complex world with many unusual relationships that exist between the inhabitants here. The grouper has found a resting spot in a large barrel sponge. The sponges are animals, although they are rooted in place, unable to move. They draw sea water in and pass it out, filtering nutrients that they consume as food. The gentle water flow may be enjoyable for the grouper as it also enjoys the concealment from predators and their intended prey. Barrel sponges are the longest living animals on the planet, occasionally reaching 2500 years.
This grouper is involved in a mutually beneficial arrangement with the small wrasse that darts in and out of its mouth. The wrasse is known as a cleaner fish and they hide among the corals and sponges until they are called into action. A larger fish such as this grouper signals the wrasse by tilting upwards and opening its mouth wide. The wrasse trusts the grouper in an age old contract that provides the wrasse with food as it cleans the teeth of the grouper. This benefits the grouper by preventing rotting material from remaining in the mouth, causing infections and sores. The grouper gets free dental care and the wrasse gets a meal. The grouper will not break the trust of his little friend.