Lots of good opinions above. Fresh SW greens and vitamins, like Selcon go a long way. Some angels are going to better that others; IMO, I wouldn't put a Flame or Kirk's CB in a tank without LR (or a good grazing substitute., as an example. But that's just IMO and IME. Here's a neat trick, if you find the right place to do it. Fill a 10 gal tank with used tank water, put in some safe rocks or LR rubble and put the tank in direct sunlight. I even keep a bright desk lamp on the tank 24/7. Nutrients need to be high, so a few food pellets or leftover frozen food now and then helps. No heater, filter, or even circulation. I keep the rock farm completely covered (except for a tiny space) with clean glass. An unbelievable amount of algae will grow on the rocks under these conditions and your angels will love it. Rinse the rocks well to remove accumulated gunk. I kept several angels this way before LR was even readily available; I even raised an Emperor from juvi to big adult without it. No big deal, just showing it can be done. But my last word on this subject is always that LR is best, just not always mandatory.