I started out with clear tubing found at Menards, mainly because it was the right inside diameter, and we felt it was the most stable. Well, found out clear is not good, lets the sunlight in, which lets algae grow inside, which can clog. So, toward the end of the summer, I replaced it with really cheap (so cheap if it cracks this winter, even though I've drained it, it would be very easy and cheap to replace) sump pump tubing, I think that's what it was called. The bad thing about what I bought was that you HAD to use the part that was made to fit to the fittings, which is only every 10' or something like that. Turns out that was perfect distance for my stuff. It is black and flexible tubing, ribbed type. I bought some at the end of the year on clearance that was solid black more rigid tubing, made by a pond company, but there was no way it would fit the fittings that store also sold, and hard as I tried (soaking the ends in hot water, cutting the end to make it wider to fit, etc.) I ended up returning it all and getting the flexible ribbed type. It was VERY easy to work with, but as I said, you have to use the "joints" every 10' to put on your fittings. You probably have something better where you are. Just make sure that the pipe/tubing will fit onto your fitting pieces, or you will be in a living hell when you get home, like I was! That was the most frustrating day! I thought I was doing something wrong SURELY, but turns out others had tried that other tubing and had the same problem.
In the end, whatever works best for you, THAT is what you will use. Remember that if you bury your tubing in your bog, that part will stay there, and if it gets a hole, no problem, as you will be making holes in it anyhow. I put a connection just outside my bog, and took that piece of tubing off and drained it and put it inside for the winter. Same thing for my waterfall, just unhooked it from the DIY Skippy filter, hung it over to drain, unhooked other end from the pump and since it was downhill it naturally drained out. Voila! Winterized.