What could cause alk to drop?

peef

Active Member
Ok so I have a 24g nano....
Everything is healthy and everything but I have just recently started to test the ALK and it is dang hard for me to keep it up. I have 440 cal, 0 nitrites, 0 ammonia, 4-5 nitrates, PH fluctuation a little recently with ALK but 8.1 at lowest. Why would the PH and ALK drop? I have taken all the sponge out of chambers in back and replaced carbon with chemi pur.
 
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