If you have trouble with Cories, then best stay away from them. A 40 Hex does not have alot of bottom space and the Raphael Cat would do best having it for him/her self. As for the angels, if they are that size and are not having anything other than typical angel bickering, but they stay somewhat together, chances are you might have lucked out with having a male and two females. In that case your fine. They are of breeding age/size so have they ever spawned in the tank? I'd leave them alone unless you suddenly see two pair off and start harassing the third. The tannins are natural in waters where angels are from. I actually use peat balls and almond leaves to add tannins into my 220 gal tank. If the color bothers you either carbon or purgen will remove it. Purgen works the best the fastest. I had a piece of driftwood that literally leeched over 5 years in a tank. And I mean it leeched till the water was brown! In pieces like that no amount of soaking, boiling, or anything will do any good. Don't know why. And yes, tannins act as a anti-bacterial and anti-fungal so its not a bad thing. My water is yellowish when I do a WC but to look in the tank you really can't see it. Something else you might want to consider, you have angels that stay in the middle to top area of the tank, a Cat that uses the bottom of the tank, so why don't you consider a small group of 6 tetras to swim in the mid strata of the water (that is unless Raphael Cats eat smaller fish). Something like Lemon or Diamond tetras would be good. Plus they usually are not fin nippers which you have to watch having angels. They would add some nice schooling movement to your tank. Hope this helps.
