I have a newly stocked 55 gallon tank - about 3 days now. it has a beta, 2 angels and a plecostomus in it. I have been reading since i got the fish that angels can be tricky to keep, and can be easily killed off by sudden temperature changes. I have the tank set at about 79 deg. F , my question is what is the best way to change water without dropping the temp too much. the room temp is normaly around 75 in summer 65 at the lowest in the winter (i dont run the heat much) should I boil a pot of water and mix with the room temp water to bring it close to 79? or does it really mater? and also how much water should i change out at a time?