I wouldn't worry so much about getting something to clean the tank, since it's only a 3.5 gal you'll have to do cleaning anyway. Just wanted to point out that even ghost shrimp can be fun (if they survive :)). I have one in a four gal with my rosetail betta, and during feeding time, he'll scamper up to the top and steal a pellet. It's pretty amusing. Apparently he doesn't feel like waiting around at the bottom anymore!
If those cherry reds work out instead, that would be very cool. I agree that it's fun to have some color in there. Good luck!
Aegean, male butterfly HM
Iota, male purple salamander plaket RIP
Atomic, male pale mustard gas rosetail