An t-iasg said:
As I plant my tanks more heavily than they were before, I'm wondering if my
KH is going to be ok. Well, it's probably not
and overnight I don't want the pH to swing.
I wouldn't be as concerned about an overnight swing as I would about having a dramatic drop to a very low pH that stays low.
I read that you can add baking soda to raise
KH without affecting pH,
Actually you can't. If you add baking soda (sodium bicarbonate) you have increased the
KH or bicarbonate buffer and the pH will rise...the amount of the rise is dependant on the increase in the
KH, but if you increase your
KH from 1 to 3 you will see a rise in pH too. You could add a very small amount of baking soda and not be able to see the rise in pH with a pH test kit, though it would show with a good pH meter. Adding baking soda will not increase the
GH reading...although the
TDS has increased. For some soft water fish the increase in sodium is worse than an increase in calcium and/or magnesium (the hard water constituents). But for most fish the slight elevation in sodium is unproblematic.
Seachem Excel's affect on pH and I'm uncertain on how to proceed.
Excel shouldn't have any effect on pH.
Some important points to remember:
CO2 concentration in an aquarium doesn't depend on the other things dissolved in your water. (many folks think
O2 levels and
CO2 levels are linked...they are independant of each other)
KH is the amount of bicarbonate
pH is always set by those two (
CO2 and
KH)
A stable pH depends on both being present in reasonably comparable quantities.
Plants CAN'T remove
KH if the
GH is low. When plants do remove
KH the pH becomes very high (8 to 10) and a deposit of calcium carbonate forms (biogenic decalcification) and both
GH and
KH drop.
So, generally speaking, plants during photosynthesis will remove
CO2 from the aquarium water, removing
CO2 will cause the pH to increase (
CO2 forms carbonic acid...a pH lowering acid uneffected by the buffering mechanics that
KH has on other acids). Fish respire ammonia/ammonium from their gills, combined with solid wastes being broken down by bacteria an you have lots of nitrification depending on the number and size of the fish and the amount and type of fish food given. Meaning, it's fairly easy to overwhelm a low buffer with the acids produced within the tank. Healthy plants generally help remove acid cause issues within a tank...but new plants that may not be healthy can and do exacerbates the nitrification problems.