[Sk8r]

Your temp is too low [should be consistent 80] and your ph is .1 high, but more importantly, and worse news, I know, for you: tangs and angels do not live in a 40 gallon tank. You need twice that for these fish, which have an incredibly high oxygen requirement and need room to run to oxygenate their bodies.

In a 40 gallon, look at a place like liveaquaria.com marine fish and look for nanofish. Those will do much better.

Likewise read the two * threads at the top of this forum: they are long, but they will give you help to get your tank in order.

I don't know what books recommend reef temps as 75. Most species commonly kept in reefs prefer it around 80.