I don't think it will hurt anything as long as there are no sharp or jagged edges around the openings where it was cut, if there are to may you want to sand it or heat it to a rounded/soft edge.....just my 2 cents
Stick with the white, if my knowledge this is for potable (drinking) water and should be safe.
The black is for sewer and less worry if it leaches anything.
I am sure there is a plumber among us that can set things straight.
agree with the white, it's what we used for pools and fountains and fishponds for the filter systems and UV damage is minimal as I have seen pipes that have been in the sun for 20 years that were just fine
I use the white pipes in my tanks. Makes great hiding spots for catfish / cichlids. Also you can sand them take off all sharp corners and cover in silicon or resign and cover with either sand or gravel for a better natural look. It is best to cover it as the UV light will damage it over time but its not found to break down too much.
Both the white and black should be safe .. There is no danger of uv damaging the pipes in aquariums .. UV penetrates very little in the water, and would harm the fish, plants and inverts long before it could degrade the plastic . When cutting sections of pipe for projects , just smooth the edges so there are no sharp spots that could injure the fish .
Everyone uses the white to plumb their salt water tank. And if you've ever met any hardcore saltys out there.. they are very paranoid about stuff getting into their tanks.. if is good for them.. then it'll be fine for FW for sure.