It really depends on why you took it out in the first place! When you say "back in to a pond" I assume you are referencing to having taken them out for a specific purpose or reason, in which case I would say put them back in when you are ready the issue has past. If you are talking about how long they can be out of water, I'd say max 4-6 hours.
My guess it that it is not going to be a happy little turtle! I would recommend a MUCH larger tank or a fenced-in outdoor pond!
you can but it likes it in the tank too
Yes, pond hyacinth is fine. Turtles can eat that plant.
I suppose you can but any benefit no. Get different water plants
Yes, they will happily eat the eggs wether it was theirs or not.If you are breeding them it is best to leave the female with her eggs and put the male in a different enclosure.
Its really a gamble to put any fish with a red eared slider , it depends how big the sucker fish is if it is small the turtle with probably eat it , you are supposed to let them grow up together i have a sucker fish with my red eared slider but they are baby's so they have not bothered it.
a dangerous way is to put your hand in front of it. if it pulls its head back it can see you. that's why it pulls its head back. no guarentee if this will work though
Yes, I put my baby slider in a sand filled terrarium over night and feed him in water and he is doing ok
Yes you could if it in a big enough tank or pond.
what will happen is that the baby false map turtle will get along with the red ear slider .B ut it will just take a will.
I wouldn't recommend it - since the RES will view the fish as food !
of course! i have a baby red eared slider living with a big 8 inch turtle and they get along! you have to make sure they know and like each other before you put them both in the same tank