Legally a landlord cannot refuse an apartment to you because you have pets, or evict you because you have pets,
even if (and this is
very important)
you have signed a lease saying pets are not allowed! In Ontario,
any clauses in a lease that are illegal are null and void if it ever came down to fighting it with the landlord and tenancy board. Note, though, not all landlords know this (having rented for the past five years, its shocking how little landlords know sometimes), and some can get around the issue by making up another reason not to rent to you/to evict you (like saying your references didn't pan out, etc).
What I would suggest is look at places and lie/dont bring up the issue. Don't rule out looking at places just because the ad says no pets. Often they really refer to cats and dogs anyway. If you are really serious about a few places, you can do what I did and say that you had one cage of small animals (didn't tell him it was a huge double CN...) or something similar. See what he/she thinks. Even though he cannot refuse to rent to you on that basis, lying is probably not the best way to start out with a new landlord. My landlord was a bit nervous about it, but I said that they were very sweet and never smell, as I clean the cage twice a week. He gave the ok, and it turns out when he met them (when he was checking something in my apartment), he was quite pleased with them, and said they looked cute!
Another route you can go is never bring the issue up at all. Don't be afraid of signing a lease that says no pets, as the clause isn't legally binding anyway. If/when they do find out, you can take it from there. Note though, if they bring it up, I still don't reccommend lying to them, and if they ever try to take action against you, you can show them the landlord and tenancy board laws and calmly suggest that you wouldn't be afraid bringing the issue to their attention.
Sorry for such a long post, its just that I went though this a couple of months ago, and thought I would shed my knowledge.