wow thats hard to imagine..
1. sounds like that sailfin has been in that tank for a long time. he eventually got semi used to the horrible water quality, but i guarantee that tang will not make it.
2. tang police?! why would ur friend put a tang in a 29 gal?!!?
when ever i buy a fish i test the water from teh store i bought it from. SWF has 0 trates, 0 trites, 0 amm, ph is 7.9-8.0, sg is around 1.023ish
a fish that has been living in water quality at 0 trates from anywhere between 1 week and 2 months will not adjust to a tank with a trate reading of 80 and live, unless that fish is a mutant. GL.