ph spike in newly set-up freshwater aquarium. Needing advice

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I am trying to lower my pH out of principle at this point. A lot of this is simple experimentation with my R.O. unit, and trying to get an even balance. To me, a pH of 7.8 is too high for tetras, no matter how well they can adapt.
 
So does anyone use R.O. water with tap water? If so, what are your ratios?
 
Harmy, to answer your KH question, my test kit just ran out, but as of a couple days ago, the KH of all the water I added to my tank was no more than 4 degrees. That is why I mix with the R.O. water, to drop the KH and GH, to give me a low pH. I don't see how a KH that low can give me a pH of 7.8.
 
Wow, I wake up and get all these responses. Awesome. I will try letting the tap sit out overnight, but like I said, it took me three days to fill my tank. Each day I'd test the water in the tank itself, which had already sat out for a day or two, and the pH read the same at a 6.8. It wasn't until I had it all the way filled and turned the filter on that the next day when I tested it, it read a 7.8.


You may have to aerate the water while its "sitting out", surface agitation is what will cause the change in PH if CO2 is being off gassed. So instead of waiting 24hrs which did not seem to work in your tank. Try putting some water in a bucket and running an air stone or extra filter/pump in there for a couple hours to get a reading of the PH.
 
It sounds like you've got a buffer in your water other than just the KH. You might want to test for Phosphates as this is a common buffer for pH that throws off the pH/KH relationship.
 
That is an interesting theory about the phosphates. I was not aware of that and I don't have a test kit for phosphates, but I assume they make one. I don't use a water softener, but I mix my tap with R.O./D.I. water, which basically is the same thing. Here's a question for you all...why is it that when I mix my tap with my R.O. at lets say 50/50 ratio, that my hardness drops, but my pH stays almost exactly the same? I am removing KH with the R.O. water, so why doesn't the pH drop?
 
If I were to use lets say, 1 gallon of tap and 4 gallons of R.O., my pH drops, but then I am left with almost no hardness. Basically, I am trying to find a ratio of R.O and tap that gives me adequate hardness and gives me a fairly low pH, but I can't seem to get the low pH without sacrificing the hardness GRRRRRR. How much hardness do I need?
 
well a kh of 4 and a ph of 7.8 means you have a co2 of 1.9. with a normal tap of 3.0ppm of co2. lowering of the co2 by the ro water would indeed rise your ph.
 
that CO2 chart is meaningless if you have phosphates in your water. I have also found that many water companies add phosphate to tap water to raise the PH so its not corrosive.

I got a test kit for phosphate but I'm not sure its accurate I have yet to test it against a calibrates source. It shows my tap water has 2.0 phosphates
 
Well, I am thoroughly confused as to what to do at this point. I don't know how to lower my pH without taking some of the water out of my tank and replacing it with straight R.O., but if I do that I will drop my hardness levels down, and I don't know if that is such a good idea.
 
I guess the main question that has not been answered here is, Why do you need or think you need a lower PH?
 
I guess it's like the rich person who thinks he needs 10 cars :) For two reasons, really...The first being that my focus is on tetras. Anything from Glowlights to Neons, to Lemons to Bloodfins, and this fish prefer a pH closer to that 6.8 range that I had going before my pH spiked. Secondly, at this point with all the experimenting I've been doing with my R.O. unit, it is simply the principle of the matter. I'm assuming that the fish I want to do will 'live' in my current pH, but a 7.8 for tetras??? That is just too high.

I want to know why I started with a 6.8 and now it is a 7.8. A spike that large just does not make sense to me, whether it is phosphates or CO2. What would you recommend I do to drop my pH at this point?
 
Another big part of this is simply trying to learn about water chemistry.
 
Another big part of this is simply trying to learn about water chemistry.
Thats perfectly fine and encouraged!

Well peat is good to lower PH, can be put into your filter in the tank. Or You can pre filter the water through peat before putting it in the tank.

I guess your just going to need to do some testing of KH/PH and letting water sit/be agitated until you find a good solution as I'm not that up on all of this.
 
Does using peat lower the pH by removing KH from the water?
 
SpeedEuphoria, thanks for responding to all my questions. I appreciate it. The first guy in that article said he dropped his pH from a 7.2 to a 6.8 with the peat. My concern, if I used the peat, is that it would take my hardness away. Since I am already mixing with the R.O., my hardness is between a 3-4 for both my KH and GH. I'm not even sure if these levels are sufficient, and if I used the peat, then I'm afraid I'd lose it all. I started another thread asking what an appropriate amount of KH is necessary for a tank. Basically, what is the least amount I can get away with having that would still be safe, and would keep my pH stable. My hardness currently seems like it is at ok levels. It's just the higher pH that is the concern.
 
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