Hey guys, i'm new to the forum and i've searched around but could not find anything on the topic of angel fish issues. My dad got two large "semi aggressive egg layers" angelfish just before the new year came around. one is all white and the other marbled black. the tank is a freshly rebuilt 55g tank. new gravel plants and decorations, i cleaned the gravel and everything put in the tank and we hooked up the filters and let the tank sit and run for a couple days before putting some fish in. the water tested about 7.4 so i used pH Down to lower it more. I used safe start to get the tank going safely. After nearly 2 weeks the angels were alright, slow movers and nothing really to watch and didn't eat much tetrafin. They started goign crazy the other day. the black one was laying on the bottm still breathing and the white one was at the top gasping for air. i hooked up the air tube for the penguin pump to put oxygen into the water because i didn't have it hooked up previously. the temperature has been over 75 degrees. When my dad checked the tank today the white one had died and the black one is still holding onto life gettin kicked around the tank. He brought him home to our 150g with a bunch of community fish in it (gouramis, tetra, pictus cat, snail, dalmation mollies, sunburst mickey + pleco) and all my fish are doing great. what could cause my fish to be so close to death and still not die. and i dont want it to effect my fish here at home. would the lack of oxygen do brain damage to the fish?