any idea to prevent internal bacteria, dropsy..?

[gooner]

lol.. since after the lionhead swim bladder.. now i got two fish having internal bacteria.. dropsy.. jus notice it today with bloating stomach and stand up scale.. it is pearl orlanda with normal fatty body which make me miss see it as internal bacteria lol.. last time i have been putting the internal bacteria medicine, but in the end of the day, i lost them too.. i m frustated of losing fish in such a way.. any idea to prevent it? and what other thing that i need to do despite of putting the fish in a tank with anti internal bacteria? seem like no use at all.. i have try it lotsa time heh.. one gona die by tomolo.. hopefull the second will cure by the advice given by you guys..

[gooner]

another, the water is so clean that i have change 30%water everyweek with cleaning the water filter.. i dun think itis becos of the water quality.. which make them got internal bacteria..only the ph.. cos after the dew day, on day 3.. the water get bit acidic.. i ignore it still weekend to change water..