The smaller horned nerites make a lot less of a mess then the larger nerites, I'd go with 3 or 4 in a 10 gal tank. If you get larger ones go with 1 or 2 unless you enjoy vacuuming your tank 2 or 3 times a week....
I believe the snail I'm looking to buy is not of the smaller variety, because I saw similar ones listed as "little".
Skye - My first betta, a blue halfmoon. SIP
Tsuki - Current betta, a spirited halfmoon
There's no difference between "Thorned" and "Horned;" both are[I] Clithon Corona/Diadema[/I . Sun Thorn are Clithon Donovani and are bigger. Thorned/Horned are .25"-.50" when mature. Sun Thorn are .5" to 1" at maturity.
I have a coupon code for APF. If you decide to buy from them send me a PM.