Okay I dont like the tang police either and I will be the 1rst to admit having a small 1.5" hippo in a 30 gallon (only for two months, been 3weeks so far. the big tanks coming, I'm just collecting the filtration equipment and such first). my rational (perhaps ill advised) is if you can QT a grown tang in a 20 gallon tank with PVC for shelter for 4-8wks two months in a 30 gallon full reef with rocks and such cant be anymore stressful psychologically. But I have to say going from a 10gallon to a 24 gallon is ill advised. even disregarding the tang a) there is hardly anything you can keep in a 24 gallon that you cant keep with what you already have b) if you are successful with a 10 gallon you arent going to learn ANYTHING by going to a 24 gallon. Fact is smaller is less forgiving because small changes or mistakes affect water parameters much greater with a smaller body of water. most equipment that does wonders for large tanks dont fit small tanks making it that much more harder on the maintainer. small tanks are cheaper and require less elbow grease but are harder to keep water quality prestine. c) yes the tang, you can rationalize to yourself that a tang is fine in a 10-24g for up to close to a year but EVERY credible source of information says otherwise, even for small tangs. So you can do it so as long as you dont find comfort in knowing other people do it and say its fine or because its small and appears healthy. This is how everybody rationalizes about things they have in their tank they really shouldn't. I'm in same boat as you, I only said something because your upgrade plans arent much of an upgrade.