If the tank is large enough and the turtles are compatible. If there is aggression, separate immediately. The general rule of thumb is 10 gallons of water for every inch of shell. So, if you have two 4 inch turtles, you need at least 80 gallons of water.
Bottom walking turtles don't need that much water because they don't "swim" (they can, but generally don't), and my general rule of thumb for musks is 10 gallons for every 2 inches of shell.
No. Not unless you're prepared to take care of all the baby turtles they will have together.
Nothing, they will probably become friends. Female turtles are very compatible. Now, you don't want to have multiple males in a tank with out more than enough females to go around because they will fight.
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.
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.
Maybe. It depends on the tank conditions. They can breed in the tank but the female will not lay eggs in the water so if you are wanting them to breed, you'll need to make an area so the female can get out of the water and into sand to bury her eggs. If your female does lay the eggs in water they will most likely die unless you remove them within 2 hours and place them into a heated place in the same position you found them. From my experience I have not been able to hatch any eggs. My female has a land area with sand and a lamp yet she always hatches them in the water and by the time I see the eggs they are unhatchable.
turtles need to swim, live, everything in water and toads need water but don't live in it. . . . . Also the turtle could possibly eat the toad depending on size hahaha
Yes they can as long as you follow the rule about 10 gallons per inch of shell for all turtles. For instance= 2 2 inch turtles need 40 gallons not just 20. Make sure the turtles are near the same size and you don't have two males or there will be aggression. Also, if you have a male and a female prepare for them to mate. Also, the tank gets dirtier a lot faster.
no RES turtles are fresh water turtles
Yes, they can live in dry land or in water :)
yes
for two males a ten gallon tank heavly planted, two females 1 gallon, male and female same as first one
No, not really, you need mostly water and a few rocks out of the water to bathe on, a big tank depending on how many turtles you keep, because they get BIGGER than you think they do! you also need a light and no other smaller fish with it.