i need some insight on ph problems. im currently way overstcocked on a 55 with s. American cichlids and C. american ciclids. they arent huge at the moment but im housing 17 chiclids in a 55. ive had to hold on to some fish for a couple of people ones moving and one needs a bigger tank. my prob is my ph is only stable at 6.8-7.0 for 2 or 3 days at tops. after that you blink and its at 5.0 !!!!! or at least thats as low as the kit goes. im currently using an old school aquasupreme by danner. the fish arent showing any signs of stress or breathing heavy and their colors are beautifull when feeding. i feed them a wide variety or food. theres a little tail tagging now and then but nothing extreme right now. my other water levels are fine. my question is, can an over stocked tank drastically affect the ph like ive mentioned. i do routine water changes 10 gallons every week and grav vac the substrate. ive kept fish for about a year now and ive been fine for the last 7 or 8 months no deaths stable water levels nice growth except for this tank now,my other tanks are sweet. would more filtration help keep a ph of 6.8 - 7.0 which it is after water changes or should i perform bi weekly changes. to be honest it looks like a few of the fish i got from a friend wont be leaving my tank soon as he still hasnt bought a bigger tank. an old timer at a mom and pop fish store said the ph could be dropping from excessive"****" for lack of a better word. more fish more **** lower ph those were his words. i know an "unsuitable but stable ph" is better then a yoyo ph. i have 4 tanks already im not buying any more unless i start charging admission at the door and im well aware of the use of buffers being a temporary fix not a solution. if need be id by an extra filter if thatll work im not sure however. what should i do?