Triggers (how many? compatiblity?)

1) 1 they don't play well with others
2) anything bigger than they are , their tank mate also needs to be able to stand up to the trigger .
3) and any other invert you have in the tank it might take them a while but, they will give them time.
Triggers are great fish but they have major attitude and most of it's well bad. That's not to say that they aren't really interesting fish with a lot of personality. They do have some pretty special needs like tank mates that can take the abuse that most likely will dish out. Also if you are going to put another fish in with a trigger IMO add the other fish first and make sure it's a lot bigger than the trigger. You also should watch your fingers when you put them in the tank they have sharp teeth and aren't afraid to use them on you or pretty much anything else that you put in the tank. I'm really not trying to discourage you but, they really don't play very well with others.
hth

Welcome to Aquaria Central! First off, I would say look into why the Tangs died of ich. Yes, tangs are susceptible to ich but only if conditions aren't to their liking. I have 4 different Tangs at the moment and never have problems with ich. That's where I would start. Yellows and Blues are pretty easy Tangs (Blues are kinda susceptible) but the biggest thing to Tangs is to wait for at bare minimum 2 months from set up date to add but is better to wait at least 6 months. As to Triggers, depending on the species (most of the ones you listed do play well together, when small at least). I would only do 1 Trigger in your tank, they can be territorial. I would nix the Niger unless you are prepared to purchase at least a 180g for their eventual almost 2 foot size. I would say go with the Huma, they do best in smaller tanks. Possible tankmates are a Tang of some species, a med size Angel, a type of Thalassoma Wrasse, or some Clownfish or Damsels. This is a list to give you some ideas, I would do 2-3 other fish tops. Anyway, hope this helps and again Welcome to Aquaria Central!

Yes, most puffers are easy to take care of and so are their cousins the file fish. Lots of these guys get pretty big so please look into their requirments and adult size prior to purchase. As to your cleaning crew well the puffers will pretty much eat anything that the trigger doesn't . They souldn't bother each other though the puffers are toxic and the triggers don't take any crap. To answer your last question no you don't have to do a 100% water change if your puffer inflates. Just make sure you don't take it out of the water and that the lfs bags it underwater. It's bad for them to get a belly full of air . They have a very hard time getting rid of it.
HTH
Chris
p.s. You might be able to get something of a clean up crew if you get a larger sized fighting conch. Even then they might either harras it to death or chew through it's shell. Also you might try some of the cucumbers but, PLEASE be aware a lot of them are very toxic and might nuke your tank if bothered by your fish. Also you might have a bunch of small life hitchhikers from your l.r. that may be able to establish a clean up crew if they have enough time to get well established . If anyone else can think of anything else please chime in.

Pretty much any type of invert that is Toxic would be safe to use, unfortunatly because they are toxic if they die they can poison the water really fast.

Just a small point--most file fishes are not easy. They naturally graze on corals, and very few survive in an aquarium for long, simply due to inadequate and inappropriate foods.

I would not go with more than one trigger. A huma would be fine, though they really can become aggressive over time. Mine used to be fine, but now is very nippy and has drawn blood on at least one occassion. Depending on the type of puffer, they to can be nippy and do some serious damage. Very few cleaners will survive, so plan on either doing more cleaning in the tank or replacing inverts regularly. I have a striped burrfish in with my trigger currently. The burrfish knows the trigger is tough, and is careful to stay away from the triggers sleeping spot--though he will steal food from the trigger, and has his own area in the tank staked out. Both are easy to care for and feed (raw, shell on shrimp, plus other crunchy seafood for variety), though cleaning the tank requires nimble fingers and a look out. With many puffers, it is crucial that they get lots of crunchy foods, like shell on shrimp, mussels, cockles, snails, etc, to wear down their beaks. Without this variety, their beak will overgrow and can eventually kill them.