Dwarf puffer fish my friend. They are small cute and they have wonderful personalities. It is loads of fun to watch them hunt for snails. They are a slightly sensitive fish however so you'll need to cycle your tank first. They also dont mix well with other fish, however i have had some very good luck with my ghost shrimp and ottos. The weekly water changes that they will need are well worth it.
What exactly are you thinking of as a 'predetory'. Most fish that eat other fish are for 55G and larger tanks.
If you want something that's a little bit aggressive (particularly at feeding time) the dwarf puffer might be a good choice or you could go for a school of black skirts - my little guys seem to think they're pirahanas any time food hits the tank.
yea i know, im cycling my 10g right now with feeder fish i also have some of my original tanks gravel and plant in their, but i was wondering if i need freshwater salt for puffers or instant ocean salt or just strait declorinated water
ive been doing research on dwarf puffers because i want one in my 5 gallon and yes you can put a dwarf puffer in a 5 gallon with an oto. Thats pretty much the only tank mates you know you can get and the puffer will leave it alone.