This may mean that you are over feeding your fish and they cannot finish what you have put in the tank; reduce the amount of food you give each feeding, and make sure you clean the tank regularly
Yes, urchins are considered "cleaners" and will scavenge the bottom of the tank for food.
food flaots
its possible but i have a crayfish who his food is floating he gets it but no they can not get out cause they are use to the water
Yes ghost fish can eat the same food as other fish, if the food falls to the bottom of the tank.
Dead or dying
What happens is the food rots in the tank. This rotting/decay creates gas (Ammonia) and that will poison the fish and burn its gills. This results first in sick fish and then death.
The key to her diary is in the treasure chest on the bottom of the fishtank but you need to spill fish food into the tank to stop the fish from attacking you the food is on the shelf above the tank
Yes. Algae wafers are food that sinks on the bottom of the tank. it is food for some bottom feeders like cat fish. However, some upper or mid strata fish will eat it. Unless they're carnivores.
they eat left over fish food on the bottom of the tank (if in tank)
If the fish is a bottom feeder (catfish, plecos), the fish will search the bottom of the tank for food and possibly below the surface and will generally dwell on the bottom of the tank. If the fish is a top feeder (african butterfly fish), it will search the upper reaches of the water and possibly above the surface and will generally live in this area as well. Open water fish (tetras, rainbows) will generally live in the middle waters of the tank, but will search for food at all levels. A frightened fish will go just about anywhere as will a hiding or stressed fish.
they just settle at the bottom of fish tank
Most fish can be fed fish food. If not they feed on algi, a bacteria that grows on the seabed and plants or the glass walls and bottom of a fish tank.