I've now been to the Biodome 4 times and I have to say, disregard the negative reviews you find here.I can honestly say I don't understand them.Admission is $19.50 Canadian- not cheap but not exactly mind blowing.A AAA or CAA card will you get $4 off on admission.If you have a Montreal Transit Pass see if that gives you a discount ( there are discounts on certain attractions).
This place is great and beautiful. They've done a really good job with the Beaver Dam ( you're most likely to see the beaver down below in a glass viewing space under the dam).The tropics - the birds are above you, by and large.It wonderful.The lynxes have babies now.The St. Lawrence Gulf is wonderful.In another system there is a bat cave .In another Auks and Penguins.What more do you want ?Well there are crocodiles and a Capybara.
Go by subway - Viau.