Salt water to be even more specific.
Yes, it must be in it's habitat or the bio-film dies off.
Red Eared Sliders are water turtles so they need water but sand can be in their tank with them. Sand tends to clog filters though, so gravel would be a better option.
You do not need to take care of frog eggs in any way.
No, Frogs do not need sand to live in the water. Frogs though may elect to live in swim in sand many are just as happy to bury themselves in small pebbles, mud, or other fine substrate. This practice is to hide from predators such as snakes. If there is no predators, or species that the frog views as a potential predator, a frog will be fine to leave in the water with no substrate at all. Though the frog is safe and can survive this will likely cause the animal stress. Simply to answer in a line all frogs need to survive is a source of oxygen and a source of food, not sand.
no , crabs live in fresh water
It is beleived the get all the water they need from the blood and other body fluids of the prey they eat.
Yes
Yes, but be prepared for some cloudy water.
by water...and sand in their vaginas
Salt water...Ocean...
Few desert plants live in sand. Most live in soil which may be a sandy soil but is not like sterile sand with little water and plant nutrition.
No
They live in water where they get a lot of sand. They definitely don't live in salt water,they live in fresh water lakes for sure where there's a lot of fish.