Clamped fins is a condition in which the fish will continually hold it's fins against its body unless it needs to move. Sadly this is a cause that is associated with many with infections and diseases and is a sign that your fish is infected with some sort of disease or bacteria. To make sure that the fish has clamped fins, try checking in the middle of the day when the lights have been on for a while. If you check right after the lights are been turned on or off the fish could be still sleeping, or getting used to the bright lights.
The only symptoms of this include the fish staying in one spot for periods, having all of its fins as close to its body as possible, and in some cases, it will be resting on any object in the water including laying on the substrate.
Clamped fins are a symptom of many different types of bacterial infections and other diseases that can infect any possible fish. Due to this, there isn't much-known right from the looks of how the fish reacts beside it keeping all of its fins as close to its body as possible. Normally this is done as the fish's immune system is fighting off a parasite, and having the fins away from the body requires not only more energy but also more blood flow through the scales and muscles.
Treatment and Medication
Since this is not a specific disease or infection but a symptom of many, making sure that the water quality is perfect should be the main concern. In many cases having either bad water quality or if the water is either too hot or too cold, many fish will start this behavior to alert their owners that something is wrong. The first step would be to check the water parameters, making sure that the fish is in the correct pH levels, the water temperature is within the correct levels, and if it is a new fish, that it was acclimated correctly (if it shows these signs when added to a different tank, it could be that it is highly stressed and having a hard time getting used to the new water parameters).
Due to the way that this disease affects the inhabitants, the best prevention methods are to always make sure that you quarantine anything that you place inside of your water (this includes any plants, inhabitants, decorations, and more). Thus, when you do let them adjust to your water and you truly see how they are acting, eating and if they have any symptoms or signs, we will either start to get a better understanding if they are infected or learn about what possible other diseases they might have.