Fortuna Wolf

I've been using H2O2 as a cheap algae control chemical during the setup phase of new tanks or when the tank ecology goes out of whack. I find that its not effective against some algaes like green spot, at least not at levels that I'm willing to dose at. I usually dose twice a day until the problem is taken care of, once in the morning and evenning. Since H2O2 is so reactive it quickly breaks down after a few hours.

Bettas, Neon Tetras, Corydoras Catfish, and Guppies are all fine up to 3ml/gallon (US Gallon) of 2% H2O2.
Shrimp however, are not fine with 1ml/G, and I have not performed experiments to see what the LD50 of shrimp is, but they seem to be particularly sensitive.
Snails begin experiencing toxicity at around 2.5ml/G, and I've used it to kill snails at doses of 3.5ml/G.

I do not know the level of daphnia, but I can say that for cyclops and nematode worms that hang out in my tanks my dosing levels don't kill them all, since I can still spot a few in the tanks.

As for algae control:
Blue-green algae and green water both will be hampered by 1ml/G, and killed by 2ml/G, though several doses may be required.
Cladophora seems to require 2-2.5ml/G to kill, and requires dosing for several days. I continue dosing for several days after I think I've killed it all because spores can still remain and restart it. I have used H2O2 to successfully eradicate clado from my tanks.
Green Spot however seems to be rather resistant, over 3.5ml/G, I usually let the snails take care of this since its so slow growing.

As for plant tolerances:
I have not noticed any problems in these plants over 3.5ml/G:
Anubias, Cabomba, Myriophyllum, Java Fern, Eleocharis, Marsilea, Lillaeopsis.
I find that Valsineria is intolerant of more than 1ml/G, and its leaves will die if you dose over that (though the roots aren't killed and it can regrow, but it will take a while).
Java moss is tolerant of at least 2ml/G, though peacock moss is NOT tolerant of 2ml/G (the growing tips will survive 2ml/G and regrow, but the whole mass will usually die, and then you'll get an algae bloom. oops.)
Pelia is tolerant of at least 2ml/G - I didn't add more since there was peacock moss in the same tank.
Fissidens is tolerant of at least 2ml/G as well.

Also, due to the ability of blue-green algae to send spores everywhere and live at the waterline I find that H2O2 will not eradicate the stuff, though it is very easily controlled. Once you have it under control let the plants grow and suck up nutrients and the BGA will go away on its own.