New cistern mate for my aquarium?

I have a 55 gallon aquarium that houses 6 blue long finned danios, 8 female guppies, 2 male guppies, 2 mystery snails, and 3 spirit shrimp. I would like to add a few more tropical fish to the tank. I be thinking about some tetras ( not neons) or something unusual. Any suggestions? This is a well established aquarium (I hold 6 aquariums) and just want something different.
african cichlids
Blue gouramis
Moonlight gouramis
Tiger Barbs
Clown Knifefish
or a puffer
Definitely stick to smaller shoaling fish, similar to the size you have, over things called shark and cichlids which are expected to nip up/eat what you have.

There are plenty of other tetras, just remember the more diamond shaped they are, the more likely they are to fin nip, so look into black neons, glolites, green neons, or consider harlequin rasboras, cherry barb or dwarf rainbowfish. All these stay around 1"-2" and are happy in a big shoal, say 6-10 (depending on which you choose).
Answers:    How about a school of bleeding heart tetras? Or a shoal of harlequin rasboras? Anoter apposite choice might be cherry barbs. They do great in a school of 6 and would incorporate color to the tank.
Just about any kind of tetras would be fine. Have you tried serpae tetras?

Serpae http://badmanstropicalfish.com/profiles/...

How roughly mollies, swordtails, and/or platys?
Mollies:http://www.fishdeals.com/livebearers/gal...
Platy:http://www.oceansandseasinc.com/images/p...
Swordtail: http://www.fishchannel.com/images/articl...

Keep in mind that mollies, swordtails, and platys are livebearers and breed like no tomorrow. Like the guppy, those pictures are only just one of many kinds and colors that they come in. Those pictures do not do those creatures even-handedness!
I enjoy a 46 gallon aquarium. I find that barbs are nice and peacfull. you have the know that if a bigger fish can fit a smaller fish contained by its mount it will eat it. the barbs a small and do well surrounded by groups. you could also get a blind cave fish. they have no eyes. Rainbow sharks are a bit aggressive, but they do well in big aquariums. they pic a spot and that is their teritory, they might nib a fins but it is not unpromising. You could get a placos.
I instinctively love rasboras. I have a tank with harlequin, scissor tail, galaxy , and spotted rasboras. They are fun to scrutinize and would fit in nicely.
you could add some sharks, but make sure they are small silver sharks, they grow comparatively large but they will be ok in the size of your tank.

spawn sure the sharks wont eat the other fish in your cistern before buying them. Hope this has helped
How give or take a few cardinals tetra these r really nice,emperor tetra these are nice to.rummy-nosed tetra red nosed.
Get some bolivian rams, they are awesome fish I enjoy a few in my tank I love them they are full of life and bring along w/just about everything..They also have a glowfish now too, they are nice...
All I know is no Gold Barbs they are fin nippers
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