Terrapin Water Level?

[KittyKayx]

Hello,
So recently I started to wonder about my terrapins, one red eared male and another unidentified female.
Firstly:
How high should the water level be? I usually use 2 buckets full, it's a big glass tank. This brings it to about two centimetres over their shells.
Is this enough water?
Secondly:
Should a terrapin tank have a heater?
I have never used a heater and had them since they were tiny now they are the size of a spread hand.
Thirdly:
My female terrapin laid an egg last year and afterwards she could only use half of her body and was holding her head lopsided and her shell was also lopsided. Can you help me with why this is? It is getting better and she can now use her left side but her shell still stays lopsided.

Additional information: clean the tank every week because there is no filter, I do a full water change an put in slightly warm water. The house is kept at a constant 20 degrees, the eat on a Saturday once a week because if you feed them again they just leave it and the water goes all mucky. (I clean them out on Sundays)

Thanks for reason and I hope you can help me!

 

[lrhodes]

They need a heater. They won't eat in cold water. Because they think it is winter. You need a half water half out of water set up. So they do not have to constantly be wet. And are you sure the female is an aquatic species. Don't want to force her to live in water all the time if she is not.

You don't have to have half out of water, but at Least a pile of rocks they can climb on to get out of the water. And a higher level of water would be ideal. So they can swim around. Not just wade in the water.

I had a red ear slider until he out grew his tank. And eventually let him go in a pond.
Sorry I responded to this so late. Didn't realize it was posted in may.