<a href=showthread.php?s=&postid=11055133#post11055133 target=_blank>Originally posted</a> by rickyfins
Any regular tubing that fits the nipples should do it. I try to get something that is a little tight and heat the end a bit when attaching it to the pump. This way when the tubing cools it has a greater seal. My pump is not like those, mine pumps and will build pressure in the tubing and if there is a kink it will either pop the tubing off the nipple or the tubing will burst. The type of pump I am using is more for long distances like in my application. I could literally pump top off water up three stories no problem but with the ones you are using it is for short distances without back pressure.
The tubing you need should be at HD or Lowes for between $0.15 and $0.50 per foot
You could use the clear (like airline) tubing or get PEX which is thicker polymer tubing that can handle higher pressures but cost much more. I prefer the clear tubing as it is easier to work with and is easy to replace.
How stiff or hard the tubing is shouldn't matter as long as the tubing will fit over the nipple. Try heating the tubing on the end when attaching it and see if that helps. If it is harder tubing it is probably a better quality tubing than the manufacturer provides or sells.
I hope this helps.