I can't/won't tell you which fish to acquire, but I can answer your question on the Silver Tip Tetras. I'll just copy the profile on this species I authored on another site a few years ago.
Hasemania nana
Family: Characidae, Hemigrammus Clade
Common Name: Silvertip Tetra
Origin and Habitat: Rio Sao Francisco basin in eastern Brazil. Baensch & Riehl also include tributaries of the Rio Perus in western Brazil, and Hoedeman reports the Rio Iguassu in Brazil. Occurs in both whitewater and blackwater creeks and smaller streams away from the main rivers.
Compatibility/Temperament: Peaceful in general if kept in a decent-sized group; suitable companion to livelier characins, danios, small catfish and loaches in acidic water setups, or livebearers in basic water tanks. Prefers a light current from the filter, so other fish in the tank should have a similar need.
Diet: Accepts prepared foods including flake and frozen.
Size: Attains 2 inches, usually a bit smaller.
Minimum Tank Suggestion: 24 inches in length but a 30-inch would be preferable.
Water Parameters:
Soft to moderately hard (hardness to 20 dGH), acidic to basic (pH to 8.0) water, temperature 22-28C/72-82F.
Description
A lively and peaceful shoaling fish that must be kept in groups of at least six but preferably more. Needs room to swim, and prefers a slight current comparable to its habitat streams, so longer tanks are preferable. A good fish for beginning aquarists, and quite long lived. Colouration is a bit variable depending upon the place of origin.
Males have a white tip to the anal fin, females a yellow tip; otherwise, males are slender and brighter coloured. Easy to spawn using standard characin methods, and parents will eat the eggs if not removed. Males can be territorial and sometimes nippy, but when kept in larger groups with swimming space are not troublesome.
This species was initially described as Tetragonopterus nanus (Lutken 1875), and was subsequently also considered in the genus Hemigrammus. Meinken (1938) described the same fish as Hasemania marginata. Zarske & Gery (1999) assigned the species to the genus Hasemania as H. nana and established Meinken's name as a synonym. This genus belongs to the Hemigrammus clade, but is easily recognized from the species in the genera Hemigrammus and Hyphessobrycon by the absence of an adipose fin.
The genus Hasemania was previously considered within the subfamily Tetragonopterinae, but this classification has for some time been deemed incertae sedis [Latin for "of uncertain placement"]. In a study published in 2010, it was determined that the subfamily Tetragonopterinae should only be used for species within the genus Tetragonopterus (Javonillo, et al, 2010). Also, Mirande (2009) has proposed several revisions to the Family Characidae based upon phylogenetic diagnosis. Some genera have been moved to a new subfamily, while others are now (temporarily) assigned to a specific clade within the family pending further study.
References:
Javonillo, Robert, Luiz R. Malabarba, Stanley H. Weitzman and John R. Burns (2010), "Relationships among major lineages of characid fishes (Teleostei: Ostariophysi: Characiformes), based on molecular sequence data," Molecular Phylogenetics and Evolution, Vol. 54, No. 2 (February 2010).
Mirande, J. Marcos (2009), "Weighted parsimony phylogeny of the family Characidae (Teleostei: Characiformes)," Cladistics, Vol. 25, No. 6 (July 2009).