Also, OP, look at what I have told you before... On the same. Exact. Thread.
If you don't want to listen to us, then don't. Theoredically you could put any fish in your small 25g tank. You can. But, it's not right. You are abusing animals. We have given you answers, but you are still refusing to accept them. If you dont want too, then okay. You don't have too. Either way the fish are being abused. Even if you get a larger tank. Like I have said multiple times a tang needs at least a 6 tank. AT LEAST. Taking what, a 3 foot tank and adding maybe a few extra inches is still, not good enough. Please, at least, return the tang. It may seem happy, but how would you know? You are not the fish. You can not speak for ones emotions besides yourself. You never truly know, unless it's yourself. The tang is clearly not happy, even if it is swimming around and eating. It will become very stressed, very, very soon. Like I and many others have said multiple times already, unless you can get a much larger tank right now, then you need to return it. None of us can force you to do it, it is your choice. You need to make the right choice. I know it can be tough, but it will also be tough watching your fish die because it was way too stressed. Give it a better home, please.