PH keeps going down!

satanpie

Banana plant addict.
Aug 25, 2007
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Long Island NY
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Since I added plants in my 45 gallon the ph keeps going down. I did a 50% water change today, came back 3 hours later and Ph is yellow, about 6.0. The water comes out of tap about 7.5 around here. My 5 gallon is also always acidic even after large water changes. I added some Ph buffer ever though I really didnt want to, but i'm gonna check again in a little while to see if the levels have gone up at all.
 
i have a 40 gallon bin that i have filled with spare water, when i test it in there its high, around 7.5-7.8, then i did a 50% water change, tank ph was about 6.0. came back a few hours later and ph is 6.0. Could it be because of my plants dying and rotting? All of my fish seem healthy though, so i dont know.
 
sop what do you suggest i do the keep it from goign too low?
 
how do i est my kh? is that the hardness of the water? thanks for all the help guys!
 
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