You should get a RO
unit at some point. Whether it needs to be sooner rather than later depends on if you have a LFS
that sells RODI
water and your finances. I dont have one yet, but I have 2 LFS
that sell it for under 0.40/gal
. So i buy buckets of it every week, but that's obviously not the most ideal situation.
Sorry about the tangs- they are awesome, I agree. I don't have one either cuz my biggest tank is a 55g and most tangs need at least a 6' tank.
Tangs are very prone to ich, so if they're not happy, they can get ich and wipe out your whole tank. Not worth it, there are lots of other beautiful fish that will work in a 40g.