I use fountain pens on a fairly regular basis although I don't proclaim to be any kind of expert.
The first ink that comes to mind for someone who worries about the integrity of their notes is Noodler's Bulletproof Black. It resists pretty much everything, even bleach. If you wanted to get it off a page, the easiest way would probably be to burn the paper it was written on. It isn't cheap (£15 for a 3oz bottle on the first UK website I found it on), or that readily available here but if your notes are really important to you, I don't know of anything better for you to write them in. Alternatively, there is Noodler's Borealis Black; it seems to be pretty similar to Bulletproof Black but it can be removed from clothes with bleach.
I use Registrar's Ink quite regularly. As the name would suggest; it is waterproof and resistant to U.V., I don't remember how resistant it is to bleach or other chemical attacks but it probably isn't quite as good as Bulletproof Black in that respect. Diamine is a popular brand of registrar's ink but there are others available. Even the Diamine one will be a lot cheaper and easier to get hold of than the Noodler's inks I suggested above. All registrar's inks are blue-black but look considerably lighter when they first go on to the page, only getting darker as they dry. The one thing to take note of if you decide to use any registar's ink is that its pH is slightly acidic. This means that it is recommended that you flush the pens you use with it on a regular basis, otherwise it could cause some damage to their insides.
These are by no means the only solution to your problem, it might be a good idea to check out "Fountain Pen Network" or another pen forum for some more suggestions and reviews. I seem to recall that someone tested a lot of inks with water and bleach and posted a picture of the results, this might be useful if you can find it.