I see from another post - there is also a tang in your tank? - I might hold off based on the amount of stuff in your tank. I do not think ammonia would be a problem. Fighting may very well be. If/when you decide to add a small angel - you could add some nitrifying bacteria.
Another potential issue - is that your stocking density is getting 'high' for that size of tank - meaning that any disease, CI, velvet is much more likely to be a problem if it is introduced. One key mantra in the hobby is 'stability' - I would suggest to you that the best way to have a small tank - is to stock it appropriately - and not be constantly adding and re-adding fish. I'm not saying this to be mean - only a suggestion. I note you were planning to give the tang to your dad as well at some point?