hello thanks for your detailed reply. Yea the tank KH isn’t literally zero right now but it’s pretty damn close, test strip indicates very low.
I think at this point, we should ask ourselves what is the point of KH. Carbonates are buffers. Buffers "stabilize" pH ... in other words, if you add muriatic acid (H+ and Cl-) to someone's well water with a high KH, the pH may drop by .1 of a point, because the carbonates bind to those free H+ and lock them up via:
In the same way that if you go outside, find some limestone, and squirt muriatic acid on it, it will bubble (forming that CO2 and H2O). However, if you do that to a chunk of river rock (granite), it won't due to the lack of carbonates in the rock.
Is it ok to be low, sure - and if you want to breed softwater fish, then I would say you need to be meticulous in finding natural ways to reduce that pH. However, just to keep, I am not so sure.
My tap KH is low as well it’s around 1 degree or 20 ppm. South Florida water kinda sucks for aquariums.
Many people would die to have soft water coming out of their tap and save on RO systems. Remineralization is easier than demineralization.
I’ve already had the planted tank run fishless for around 2 weeks now, I think the cycling is basically done at this point. I doubt the soil will lower the ph any more than it has, I soaked it numerous times during mineralization.
Err on the side of caution as its a whole lot easier to wait for the cycle to complete rather than continue it with the stress of having fish in the tank.
realize that it may be more tedious to add acid for every water change, but honestly I’m willing to put in that extra work to ensure my fish are comfortable. 6.8 and 8 is a huge difference, that’s over 100 times more acidic than my tap. And to be honest I only add like 1.5 milliliter to a 5 gallon bucket of water and leave it for a few days before the water change, not too much work. It’s just unfortunate that it seems to be the only way to fix this. Anyways I appreciate your advice! Let me know if there’s anything that I’m missing!
I totally feel you, but people manipulate their pH every day with CO2 injection (and natural waters change their pH throughout the day) - increasing and decreasing the "acidity".
It boils down to what you want: the "appropriate" pH, or a bit more buffer when things go/go wrong (fish death, decay from wood, decay from plants, decay from mulm, nitrogen cycle) everything forms acids in our aquariums.
I debated with the following few lines, but I have been through the muriatic thing, and putting on those gloves, worrying if I spill on myself, spill on the floor, etc was just not worth it. If I was out of town, was I going to ask a family member to open that bottle and put in exactly 1.5 mL ... what if they are off ... ok so forget the water change while I am gone ... then my minimal KH is eaten away and our artificial system continues to go and my pH crashes anyways ... it crashes and stalls bacterial activity (low 5's) ... then I have ammonia spike ... then I need to more water changes with the acid ... or I don't ... then my fish stress ... then I go get meds ... then I ... and so on. This rabbit hole can be avoided by omitting the acid.
The ideal way to reduce that KH and get those natural waters you are looking for is with peat or almond leaf - but you want clear water. So we are at a crossroads - artificially chase the pH OR leave the water as is.
You can do either, but I have a bottle of muriatic acid that I will never use again, except for testing rocks in the wild to see if they are inert or not.
EDIT: I will add that reef tanks do add Kalk to their aquariums to increase the pH -- that is pure OH- kind of like your "pure" H+ ... so there is merit in the idea.