For a land tortoise, you will need a UV light (that provides artificial sunlight), Vegetables, substrate (dirt), and a hiding place.
For water turtles You will need all this + bugs and water.
About a 20 gallon tank.
Depending on the species, one or two. Turtles will keep growing through their entire lives, overcrowding or expecting them to only grow to the size of the tank is something that usually leads to dead turtles.
I think it depends on how big the turtles are.
Tapping on the glass of the tank !
No, a mussel or clam cannot be put in the same tank as a baby turtle. Baby turtles, as well as adult turtles will eat mussels and clams.
The turtles will eat the fish.
You can just use regular water. In the summer/warm weather, I clean my turtles' tank outside with my hose. I also use faucet water. If you'd like to know how I specifically clean my turtles' tank, please contact me or reply to this answer.
Tapping on the glass of the tank !
no RES turtles are fresh water turtles
To effectively clean a dirty turtle tank and ensure the health of your pet turtles, follow these steps: Remove the turtles from the tank and place them in a safe container with clean water. Drain the tank completely and remove any debris or waste. Scrub the tank walls, decorations, and filter with a mild soap or aquarium-safe cleaner. Rinse everything thoroughly with clean water to remove any residue. Refill the tank with dechlorinated water and add back the turtles. Regularly clean the tank, change the water, and monitor water quality to maintain a healthy environment for your pet turtles.
no they wouldn't
It is generally not recommended to house frogs and turtles together in the same tank. This is because turtles are known to be opportunistic feeders and may mistake the frog as prey, posing a risk to the frog's safety. Additionally, frogs have specific habitat and environmental requirements that may not be met in a turtle tank.