The best way to get rid of the snails:
Cut a peice of cucumber or zuchinni. Place a saucer in the tank.
Tie or elastic band it to a rock.
Pop in tank on saucer
About 1 hour later you will find most of the snails
have migrated to the peice of veggie, then just remove the veggie
and the saucer full of snails. Repeat till most snails are gone.
Or, Just use your fist and crush em against the glass when you see them.
Unfortunately most snail-acides will also kill your live plants. I dont know
of any you could use that wouldnt completely destroy your plants.
I wouldnt empty your tank and scrub it,
it would have to re-cycle, which would probably kill your platies.
I have 7 adult platies in my 75g community tank,
and supprisingly, despite all the majorly hungry fish in the tank with them,
I can fish out good sized baby platys (bout 2 weeks old)a couple times a
month from the floating plants on the surface of my tank.
What type of algae eater do you have?
If it is a chinese algae eater or a common pleco, they grow much much too big for a 10g tank.
Chinese algae eaters are also very well known for their aggression and refusal to eat algae once they reach the 5 inch mark. They grow to about 8 inches, common plecos grow to about 24 inches.
As for how many adult platies in your tank, I used to keep 15 females and 5 males in my 25g tank, but I found they reproduced too readily.
A Good Idea if you dont want to constantly deal with fry every few weeks, is purchase a small fish that will eat the newborn fry, such as a paradise fish, or dwarf gourami.