If a fish is healthy it will grow. Any 9-14" fish in a 12-18" tank doesn't make sence. Planning to put a fish in a bigger tank is one thing but keeping it in a small tank I wonder how long it will accualy live? But I guess my Cherub angel =2" must love its 120g which it swims the whole tank. I have larger fish just want to point out angles and tangs need more room. My 120g is to small for my naso and sailfin but I'm plannig a much larger tank also. I have a small naso med,sailfin, cherub,perc clown,neon gobie,manderin. We have the same fish load.