Ok lets see if I can clear up my intentions here.
How about a little history on my tank:
I bought it back in November used from a guy that did everything wrong. He had a bad mix of livestock: firetail goby, sebae anemone(which was almost clear), 8 inch Sailfin Tang that had lateral line disease bad, tomato clown, a Saddle Valentini Puffer, and a couple other small, timid fish . After I moved the tank I went about cleaning up the mess. I sold most of the fish (unfortunately the Tang and anemone didn't make it) and added some lighting (he only had a 130w pc hood with 2year old bulbs). When I first did measurements phosphate and nitrate levels were off the charts and calcuim was somewhere around 600ppm. He had very little live rock and most of the tank decorations were old coral pieces that he picked up from somewhere (I doubt at a LFS). Needless to say the algae he had was incredible!
The changes I made were to replace as much of the water as I could after the initial move and have been doing a weekly 10g water change since with RODI from a local supermarket. I don't have a TDS meter yet so I am having to trust that the water is pure. I have been mixing the salt and letting it age for 4-6 days before adding. I replaced the crushed coral substrate with a shallow sand bed and am just finishing my diy 29 gal sump/refugium. I also threw out the junk that was in the tank in the form of decorations, turns out there were about 3 pieces of actual live rock. The lighting now consists of 240w pc with an upgrade to 2x 175w MH with 2x 65w pc actinics going to happen in the next few weeks once I finish building my hood.
My water parameters now are:
PH: 8.2
alk: 9
ammonia, nitirite, nitrate, phosphate: 0 or very close to it.
sg: 1.024
calcium: 400ppm
The tank is looking 100% better than it was back in November and everything is doing just fine. I only have 3 fish right now, left over from the beginning: a scooter dragonet, a rainfords goby, and a small green goby that has yet to be identified (when I get a chance I will post pictures of it on here and see if anyone knows what it is). As for inverts I have a coral banded shrimp, 3 emerald crabs and some snails. I am finally ready with this tank to start fresh on the things I really want.
On a side note I didn't jump into buying a used tank because I wanted a cheap way in to the hobby, I have been doing African Cichlids for years and worked in a LFS during high school. When I saw this tank I also saw an opportunity to move to salt and help a suffering tank recover.
This brings me to the current topic, I think I mislead people by saying I wanted a tang to take care of algae. I don't have much algae anymore, I just like tangs and it happens that they like algae. If I do get one (which I am not sure I will) then it can eat whatever type of algae I might have that it likes. I will definitely feed it according to what is good for it.
Eventually I want to have a couple clams and a flame scallop among other things so when I think my tank is ready I will go that direction. If a tang works into the other stuff I want then great, if not I will wait until I have the correct setup.
So back to my original question, is there a tang that will grow more slowly than others or stays smaller that will be happy in a 55 for at least a couple years? I will have a 100+ gallon tank in the works by then.
Tim