High pH that I can't fix

[Darlene B]

I'm new here, so I hope this is the right category for my question.

All of my tanks, including new ones with nothing in them yet, have very high pH. I tested the well water right away, but it's perfectly normal. I assumed the gravel was the problem because it wasn't proper aquarium substrate, so I drained the tanks with that gravel, cleaned them out, and put new substrate in. Still high pH.

My platy tank has been set up for over a year now with no problems, but just this morning all of my fish suddenly started dying. I tested the water, and the only problem that showed up was high pH. Nothing in this tank has been changed recently, so I really have no idea what would have caused it. I moved the fish to a new tank (still high pH, but it was the only option), and it looks like all I can do is hope they don't die. 

I have tried pH down, adding driftwood for tannins, changing gravel, and so SO many water changes.

My questions are: Would a pH of 8.2 be enough to be killing all of my fish? What could be affecting the pH of every single tank, as the only constant is the same water source (which, again, tested at about 7.0-7.2)? Does anyone know what else I could do to lower the pH?

[laritheloud]

You're fine with a ph of 8.2 as long as you don't choose wild caught SUPER soft water fish. Source: My water has an offgassed pH of 8 to 8.2. Platies, especially, should be fine with a high pH and hard water, and that likely isn't the reason the fish are dying. Have you tested all of your other water parameters? When you changed the gravel, did you monitor parameters in case of an ammonia or nitrite spike?

Also, water straight from the tap needs to sit in order to off-gas and get a correct pH reading. You can also put it in a bucket with an air stone to off-gas and get the 'true' pH of your water. It might actually be 8.2 from the tap!

[gardenman]

The danger with a high pH is that it makes ammonia more dangerous. For your fish to all be dying, I would suspect a bump in the ammonia level that suddenly became toxic. It doesn't take much at a higher pH. A fish that died and was unnoticed for bit can be enough to crash a tank at a higher pH.  

[Darlene B]

On 1/14/2022 at 7:49 PM, laritheloud said:

You're fine with a ph of 8.2 as long as you don't choose wild caught SUPER soft water fish. Source: My water has an offgassed pH of 8 to 8.2. Platies, especially, should be fine with a high pH and hard water, and that likely isn't the reason the fish are dying. Have you tested all of your other water parameters? When you changed the gravel, did you monitor parameters in case of an ammonia or nitrite spike?

Also, water straight from the tap needs to sit in order to off-gas and get a correct pH reading. You can also put it in a bucket with an air stone to off-gas and get the 'true' pH of your water. It might actually be 8.2 from the tap!

I did check the other parameters, and everything was perfectly normal. The platy tank was not one that I had to change gravel in, so that would not have affected them, either. I have left the tap water out to make sure I'm getting the correct pH reading. The fish that die have no signs of disease or anything, so I really have no idea what could be wrong.

[Patrick_G]

Did your testing show any ammonia at all? Like @gardenmanpointed out, a small amount can be more toxic at higher PH.