Sell the eheim and seaclone and get a better skimmer
By "standard" clowns im guessing false percs/occelaris,no problem just make sure th two are a pair
2 sixlines will fight, get 1
3 grammas will fight, get 1
as for tangs,your options are very limited for them in a 55, a powder brown is not one of them.
either a yellow
http://www.liveaquaria.com/product/prod_Display.cfm?pCatId=392
a kole
http://www.liveaquaria.com/product/prod_Display.cfm?pCatId=345
a tomini (I got 1 in my 60
and probably the best suited for a 48" long tank)
http://www.liveaquaria.com/product/prod_Display.cfm?pCatId=334
or a small blue as long as you put it in a bigger tank when it grows(sell it here
)
http://www.liveaquaria.com/product/prod_Display.cfm?pCatId=330
The koles and tominis are fine in a 55 IMO,and IMO koles are kinda ugly:p but tominis are a lot better looking in real life.:goldfish2
I wouldn't put a yellow but some will disagree so I showed it to you
and blue regals are often found very small and can even be in a nano while they are like that but they really need at least a 6' long tank when they grow.
and you will have a hard time mixing but if you want, a small blue would probably get along with any of those, the kole and tomini are very simialer and would be the combo that is most likely to fight,but two tangs is a big bioload,they're very active fish
edit: oh and this is my opinion,some will say a 6' long tank is the bare minimum for ANY tang and others would put them in 36" tank.
