Number of algae eaters

Could someone give some advice on how many algae eaters is too many? I have
a 48 gallon planted tank. The plants are just getting going. I have some
red brush algae starting up and I would like to get an SAE to help with
this. Just how much algae does an SAE need? Would it be a good idea to get
two? I have 4 otos already that seem to eat all the time. I don't want to
end up with starving fish.

I'm also interested in Malasian Trumpet Snails. I understand that these are
good for the substrate and also eat waste in the gravel. But they seem a
rare commodity around Vancouver. Can one mail order snails as well -- or
does anyone know of a source in the Vancouver/Seattle area?