Of all the tetra species, the Pristella gets my vote as the best all around, particularly if you're into longevity and low-maintenance fishkeeping (i.e., scrubbing algae and changing a little bit of the water once every five or six weeks). After saying goodbye to my last Rasbora (another active and hardy schooling fish) four or five months ago, I added a dozen of these beautiful semi-schooling fish to an existing 265 liter community tank comprised of a handful of Praecox rainbows, cherry barbs, corys, a gourami and a flying fox. Knocking on wood, I have yet to lose even one. Although they don't school very tightly, these docile fish almost always hang around the bottom third of the tank, which balances well with the free-swimming rainbows and barbs. At feeding time, they will hop and dart as a group towards the end of the tank where feeding takes place, almost as if they're playing follow-the-leader. If you buy them small, they grow quickly; most of mine have grown from roughly 2 cm to 4 cm in a matter of months. Unlike many of the more popular characins which require soft, acidic water (such as neons, black phantoms, serpaes or glowlights - all of which I've had at one point or another with mixed success), the Pristella thrives in 24°C water that tends to be both soft and alkaline, which is a good thing: I've learned over the years that I'd much rather spend my time watching my fish than fooling around with the water that comes out of the tap, and the Pristella allows me to do quite a bit of the former without having to do any of the latter. The fact that they are as beautiful as they are distinctive is merely an added bonus.
I have six of these fish in my 75 liter. Tank with 2 swordtails and 1 angelfish. They all get along very well. The Pristellas stay nicely schooled up and enjoy following each other through bubbles from air stones. I rate these fish as excellent.
The Pristella Tetra is one of my all time favorite schooling fish. Although they keep a relatively loose school, they do tighten up when their more aggressive Angelfish tankmates are in breeding mode. My hard and alkaline tap water seems to suit them fine, as the initial school of 9 fish I put in my 200 liter planted tank is still thriving after 2 years. They can be shy at times, hiding behind plants and driftwood, but come out eagerly when feeding time arrives.
I have three pristella tetras (along with several other fish) in a 75 liter tank. They quickly developed very vibrant coloration, and are voracious eaters. They are not aggressive at all, but are extremely fast, active swimmers, and are like torpedoes at feeding time, so you have to make sure that your other fish are getting enough to eat. For this reason, I don't think that I personally would get too many of them, although they're great, hardy little fish, especially if you like fast moving, non-stop swimmers.
I have 12 pristellas in my 80 liter long heavily planted tank, which also houses gouramis, corys and glowlights. I bought them in groups of 4 every two weeks 2 months ago. I noticed 4 schooled fine, but when I had 8 in the tank, schooling was much more satisfactory to my liking. They are always schooling together, where one is being the leader until another changes it's course of direction. Their yellow, black, and white tip fins set off an amazing display of pure beauty swimming past various plants. Also, their brilliant red tail fins stand out against the blue gravel and background in the tank. The glowlights occasionally school as well, but branch off in the open space in front of the tank. All in all very peaceful community fish, no hierarchy display of any sort among each other. I highly recommend to anybody who wants a nice group of schooling fish, without the worries of size being a factor later on.
I have a school of 8 Pristella Tetras in my 110 liter tank, and they are fabulous little fish. They were originally used to cycle the tank when new, and showed themselves to be quite hearty. They all made it through the cycling process. The Gang now share the tank with an Opaline Gourami, Betta, two Yo Yo Loaches, and a Pleco. These little fish are interesting to watch as they roam about in a loose shool, and hold their own just fine with the larger fish in the tank.