Get one of these. These things are invaluable when drilling holes in fish habitat. They drill great in PVC tubing, black plastic tubing, plastic jugs, plastic pop bottles, plastic five gallon buckets, anything that is not over about a quarter inch thick for steel and even thicker in softer stuff like plastic. The Harbor Freight brand are probably not nearly as good as a name brand one, but for plastic they are completely adequate. I have drilled hundreds and hundreds of holes with them.
The smaller sizes are a lot cheaper and for small holes are the ones to use because the first step is the one to get dull first. But the bigger size is great for drilling 1 1/4 holes big enough for small BG and FHM hiding spaces. A person wants enough water flow through anything you place so the water does not become oxygen deficient or gather bad gasses in air pockets.
They do not work great in rubber car or truck tire side walls, but I did not find anything that really did work good for rubber.
Step drill for drilling fish habitat holes 
