Make sure that you pull the saw out of the groove that it'll be creating ever so often (it'll start heating up pretty fast).
Also if you can get some to stand by with a squit bottle of ice-cold water and spray the hole saw blade and the acrylic that will help too. When you pull the saw blade out just dip it in a separate glass of cold water - it'll help cool the saw blade down and also take some of the acrylic "dust" off the blade.
Finally, and I don't know if you are supposed to even do this :funny: once the blade is cool from being dunked you can pick off the melted acrylic that will have collected along the teeth. I did all of the above and got some every nice holes in the bottom of my tank. And as I had to explain to some friends, "I really did want holes on the bottom of my tank!"
Let us see every step of the way (Lotsa pictures). Im going to dose with kalk for now, but someday in the future I might like to try one. Im terrified of acrylic work (because of the cost of mistakes) but a Neilson Reactor is one of those items you don't HAVE to have so I could take my time and work on it. I would LOVE to be able to work with acrylic......