Moss and aquatic plants

How could I disinfect and clean moss and aquatic plants from the nature and their substrat?
Is better to use another substrat bought in a store? Which?
For an aquaterrarium of Triturus dobrogicus. What are the recommended sizes of a tank for a pair of them?
Any general ideas?
Could they tolerate -6ºC nigths? And wich is the maximum TºC for them?
Thank you very much

I rinse anything I pick from the world at large in aged tapwater and quaranteen for 30-60 days in a spare tank with substrate and lighting. I have no hard evidence that it does anything but it works for me. I should also mention that I never collect in areas near farms or residential runoff just as a matter of general safety.

You can desinfect moss by freezing it, but of course that kills the moss. It will remain green for some time though. As for plants i can´t think of any other way than rinsing them...but still lots of organisms, specially fungus and some parasites attach themselves strong enough to resist rinsing.
I myself don´t really care...moss, and other natural stuff will carry the kind of things the newts would encounter in the wild, so i don´t try to desinfect them.

I´d say a 60 litres tank would be adecuate for a pair or young trio of dobrogicus...since they are very aquatic you can keep them in a fully aquatic tank, with just some floating cork bark or a brick that emerges on the surface to provide some terrestrial surface.
As for the temperature, definitely NOT.Anything below 2ºC is very risky, and temps below 0 will kill them. Caudates survive to freezing temps by hiding very well in places that won´t get frozen even if the exterior temperature is very low. Mine have been ok at temps of 26ºC with a fall of temps at night. They are hardy but continuous high temps will be a threat.

Thank you very much. So finally I couldn´t have any Triturus dobrogicus becouse of the external TºC. I can´t put them inside home becouse for my parents with the T. shanjing is enough, and here in Vitoria some nigths are too cold in winter.